I think there is a slight difference in what you're emphasizing.
They both refer to female breasts, but tits emphasizes the nipples (pointy bits) whereas boobs evokes an image of the round parts.
english.stackexchange.com/users/1871/ghoppe
From Word Net Search : Boob Noun S:
(n) dumbbell, dummy, dope, boob, booby, pinhead (an ignorant or foolish person)
S: (n) breast, bosom, knocker, boob, tit, titty (either of two soft fleshy milk-secreting glandular organs on the chest of a woman) Verb S: (
v) drop the ball, sin, blunder, boob, goof (commit a faux pas or a fault or make a serious mistake) "
I blundered during the job interview" (I was not aware of the verb form, but it follows from the first noun form) Boob could also be used to refer to a person who is acting like a clown, or it could be used to refer to something that induces cluelessness.
We have a nickname for television in the US (although it's going out of fashion) called the boob-tube .
I assure you it's not because it shows porn.
Noun S:
(n) breast, bosom, knocker, boob, tit, titty
(either of two soft fleshy milk-secreting glandular organs on the chest of a woman) S: (n) nipple, mammilla, mamilla, pap, teat, tit (the small projection of a mammary gland)
S: (n) titmouse, tit (small insectivorous birds) (I was aware of titmouse but not a small bird called tit)
Tits is generally the word for mammary glands, being a corruption from teat.
That's what @ghoppe was onto with his, where you emphasize the pointy bit of the end of the mammary gland.
It's more evident on a dog or pig, where there are a line of teats (or tits).
The fact that this usage has spread to also refer to women is likely from the fact that country/urban life has comingled more of late than of years past.
The usage to associate tits with boobs however, is purely sexist.
In polite society you should mention neither, referring instead to the bosom that @Robusto mentions, or breast, but only when you must.
Bosom indicates "that feeling of your grandmother wrapping her arms around you when you're scared" and breasts is generally seen as more clinical in nature.
Generally in polite society you would just avoid references to a woman's breasts, and let it go.
When breasts are being discussed (such as in the context of bra fitting), women will often use the word "boobs" amongst themselves.
With men and men alone, tits is fine.
NOTE: I edited in response to a comment and decided I would give a little more attribution.
english.stackexchange.com/users/2161/jcolebrand
As others have said, both refer to a woman's breasts, but the main difference is actually in the connotation.
While both are euphemisms, boobs is a slightly more socially acceptable term.
Women, in my presence at least, use the term boobs; tits is more a term that men use and generally in a more lurid fashion.
english.stackexchange.com/users/3829/Paul
They're both terms for female breasts.
Women tend to refer to these as "boobs" and not "tits"; with men it can go either way, but a good part of the time they'll use "tits".
Other (somewhat vulgar and borderline spring-break moronic) terms are knockers , twins , hooters , hoo-hahs , etc.
Puritanical people sometimes call them bosoms , which is strange because bosom refers to the upper chest in general and few people have more than one of those.
By the way, to reference a woman's breasts by any term in her presence is coming on pretty strong, and in a business setting it can be tantamount to sexual harrassment.
english.stackexchange.com/users/2303/Robusto
Tit refers to either the breast or the nipple, is usually considered offensive, and refers to a stupid person in British English.
Boob can only refer to the breast, is not usually considered offensive, and refers to a stupid person in American English.
english.stackexchange.com/users/None/
I'm sure it varies by region, but in most of the US, the words "tits" and its diminutive, "titties," are used when referring to smaller breasts (A or B cup) and "boobs" is used in reference to larger breasts (C and especially D cup or larger).
As with most diminutives, the term "boobies" generally refers to smaller breasts.
While all four terms are used to describe human female breasts, there are variations used to describe other things: "Man-boobs" is used to describe the fatty tissue that accumulates on the chests of older and, usually, overweight men.
"Bitch-tits" can refer literally to the 'teets' of a female dog, especially while they are nursing pups, but in common slang it describes pointy male breasts.
This often happens to body builders when they stop exercising or stop taking steroids.
english.stackexchange.com/users/3800/oosterwal
I would just add that it is common, in the UK at least, for mothers to reply with "Mummy's boobs" or "Mummy's boobies" when asked the inevitable "What are those?
" question by their offspring.
I could not imagine a mother telling her child that they were "Mummy's tits"!
A small point, but one that perhaps illustrates the subtle social difference between the words.
english.stackexchange.com/users/317/Lunatik
I consider "tits" more offensive than "boobs".
Also, I am against the notion that tits emphasises the nipples.
That's misinformed IMO.
english.stackexchange.com/users/4129/yorksensei
In the phrases "boob tube", "tit puller", "tit spanners", "get on someone's tits" and "tits on a billiard ball", the two words are not readily interchangeable.
Otherwise, I think they are more or less synonymous.
english.stackexchange.com/users/305/Brian Hooper
As a woman, I use the word "boob" when discussing bras, often more than the word "breast".
The word "tit" is almost never used in non-sexual contexts, with the notable exception of the phrase "itty bitty titty committee" which is used occasionally.
english.stackexchange.com/users/133357/Demi
What is the difference between “tits” and “boobs”?  P.S. I'm not sure if this question is appropriate but as English is not my native language I really would love to know the difference.
Differences between slang words for breasts
english.stackexchange.com
<differences><nouns><slang><offensive-language>
english.stackexchange.com/questions/9293
english.stackexchange.com/users/887/Sergey
There is a slight difference in what is being emphasised by the words "tits" and "boobs". They both refer to breasts but "tits" emphasises the nipples more and "boobs" emphasises the round parts. Women will often use the words "boobs" amongst themselves whereas men will use the word "tits" among themselves. In general, "boobs" is considered to be a more socially acceptable term, and the word "tits" is almost never used in a non-sexual context. Some people believe there is a small difference between "boobs" and "tits", with "boobs" referencing the rounder part of women's breast, and "tit", the nipples  from the word "teat" which are more evident on other animals to feed their young. "Bitch-tits" is a term used to refer to the "teets" of female dogs, but also can be used as a derogatory term for body builders. Some people disagree with this and believe "tits" refers to the whole breast also. "Boob" in US English can mean a stupid person too.  "tits" is considered a sexist and derogatory term, mainly used by men, some believe, whereas women use "boobs" to refer to their own breasts. The dimunitive form is "titties" or  "boobies".  "Bosom" on the other hand is a more outdated term. There are many other slang terms for female breasts in English. The words are also used in other colloquial forms such as "get on someone's tits" meaning to be annoying. Generally, "tits" is a slang  term.
There is a slight difference in what is being emphasised by the words "tits" and "boobs". They both refer to breasts but "tits" emphasises the nipples more and "boobs" emphasises the round parts. Women will often use the words "boobs" amongst themselves whereas men will use the word "tits" among themselves. In general, "boobs" is considered to be a more socially acceptable term, and the word "tits" is almost never used in a non-sexual context. Both terms refer to female breasts. Boobs seems to be more socially acceptable and more used by women. Tits may be more vulgar. However, some may say that "tits" may refer to smaller breasts and "boobs" may refer to larger breasts.
Both words refer to female breasts, but some say that  "tits"  emphasizes the nipples whereas  "boobs"  evokes an image of the round parts. Women tend to use "boobs" and not "tits". Men can go either way, but a good part of the time they'll use "tits". "Tits" may be considered more offensive than "boobs", which is more socially acceptable. Both words refer to female breasts but differ in emphasis. "Tits" may be more offensive and is used more by men when talking with other men. Women are more likely to use the word "boobs", and it is considered less offensive.
With men and men alone, tits is fine.
With men and men alone, tits is fine.
Only a slight difference between "boobs" and "tits" referencing shape of female breasts.. Other uses of similar terms, referring to female breasts but also with other meanings Both refer to female breasts but "tit" is also a small bird. S9: (either of two soft fleshy milk-secreting glandular organs on the chest of a woman)  S: (n) nipple, mammilla, mamilla, pap, teat, tit (the small projection of a mammary gland)   S10: S: (n) titmouse, tit (small insectivorous birds)   (I was aware of titmouse but not a small bird called tit)   S11: Tits is generally the word for mammary glands, being a corruption from teat. S12: That's what @ghoppe was onto with his, where you emphasize the pointy bit of the end of the mammary gland. S13: It's more evident on a dog or pig, where there are a line of teats (or tits). S14: The fact that this usage has spread to also refer to women is likely from the fact that country/urban life has comingled more of late than of years past.   S15: The usage to associate tits with boobs however, is purely sexist. S16: In polite society you should mention neither, referring instead to the bosom that @Robusto mentions, or breast, but only when you must. S17: Bosom indicates "that feeling of your grandmother wrapping her arms around you when you're scared" and breasts is generally seen as more clinical in nature.    S18: Generally in polite society you would just avoid references to a woman's breasts, and let it go.   S19: When breasts are being discussed (such as in the context of bra fitting), women will often use the word "boobs" amongst themselves.   Boobs is more acceptable term, "tits" is more vulgar. Some disagree that "tits" refer to nipple area. S0: As others have said, both refer to a woman's breasts, but the main difference is actually in the connotation.   S1: While both are euphemisms, boobs is a slightly more socially acceptable term.   Both terms for female breasts. "tit " can refer to "breast" or "nipple" and is considered offensive in UK English, whereas "boob" also means a stupid person in US ENGLISH Dimunitive forms are "titties" or "boobies" Often referencing female animals, mainly dogs, but often a pejorative term for body builders "breasts." Other uses of "boobs" and "tits" have different meanings and the words are not interchangeable The word "tit" is mainly used in a sexual context, except fot in "itty, bitty, titty"
Both terms refer to female breasts. Boobs seems to be more socially acceptable and more used by women. Tits may be more vulgar. Some may say that "tits" may refer to smaller breasts and "boobs" may refer to larger breasts.
Both words refer to female breasts but have a different emphasis. "Boobs" is more commonly used by women whereas "tits" is more commonly used by men when talking with other men. "Tits" may be more offensive than "boobs".