Question: I have this simple question on Kiswahili, a Bantu language.

As you know in english, we can not always define morae. it's completely different from Japanese morae system.

But when I learn Swahili, sometimes there appears the term morae for the explanation.

So, is swahili (and many other Bantu languages) actually mora-counting language??

I mean, I wonder if we can always define morae consistently in Swahili or not...
It seems like the concept of morae is required to describe accent patterns in swahili, in my opinion. 
But how do you guys think?

Answer: 
In essence, Swahili stress has two rules:

* If the word is shaped like `NC(C*)V`, the first nasal is syllabic, and stressed. (For example, *ḿbwa* "dog", *ḿtu* "person".)
* Otherwise, the stress is on the second vowel from the end, and there are no syllabic nasals. (For example, *kusóma* "to read", *nitazibembeléza* "I'm going to pet them", *kondóo* "sheep".)

One way to analyze this, like you said, is morae. Nasals before other consonants count as one mora, and every vowel written down gets one mora. The stress goes on the second mora from the end, and if a nasal takes the stress, it turns syllabic.

However, you could also handle this without mora-counting at all. "Nasals before other consonants" are always either stressed and syllabic, or can be analyzed as prenasalization rather than as consonants of their own. So you might analyze *mtu* as being underlying `/mətu/`, perhaps, with a rule that makes schwa disappear (and `NC` sequences become prenasalized) whenever it's not stressed. This would also explain all the data nicely.

So, short version: as with everything in linguistics, there's no hard-and-fast right answer. Use whichever model you think explains the data most accurately and elegantly!
The term "mora counting" has a specific technical meaning, based on the connection between duration and certain linguistic units (moras, syllables, stress feet). In a so-called syllable-timed language, the duration of an word best correlates with the number of syllables in the word. In a mora-timed language it correlates best with the number of moras. The difference between the two is evident only when there is a difference between the number of syllables in a word and the number of moras -- which means, you have to have long vowels or some reason to posit moraic coda consonants. Neither of these conditions holds in Swahili, so it is impossible to determine if the language is syllable-timed or mora-timed.

However: the claim for there being *any* "mora-counting" Bantu languages is dubious. The implication of mora-counting is that a 4-mora word has twice the duration of a 2-mora word and half the duration of an 8-mora word. Instead, Bantu languages tend reduce duration of long vowel preceding the penult or antepenult (sometimes resulting in actual phonological shortening). This is more like a stress-timed system (there is at most one stress, on the penult, so the last two syllables tend to be a length unit and the stuff before – regardless of the number of syllables – tends to be a length unit, which can stretchto very many syllables)

There is not very good evidence in Swahili for the mora, since there is no vowel length, and it does not have a mora-counting tone system. The evidence for vowel length in orthographic *kondoo, njoo* is not strong: vowel doubling in spelling is a way of indicating final stress. The alternative is to say that in some words the stress is final (or antepenult, e.g. *barábara*). This is in contrast with many (don't know about most) Bantu languages which do provide ample evidence for the concept of mora. There is some confusion out there about the status of "moraicity", since there are surface-contrastive syllabic nasals in Swahili, and these are frequently called "moraic nasals". But that is simply driven by a particular theory of syllables and syllabicity, where "syllabic" i.e. "being a syllable peak" is taken to be defined as "being moraic". If you don't insist on that equation (I don't), then there is no evidence for "moraic nasals". [Ngunga and Hyman](https://journals.linguisticsociety.org/elanguage/sal/article/download/1319/1319-1939-1-PB.pdf) have a paper illustrating the problem, from Yao (a language with excellent evidence for the concept of mora).