Analysis of air bubbles trapped in fossils, such as in fossil amber, show that our air in earliest times contained about 35% oxygen. Today, the average oxygen content of our air is approximately 20%. In some larger, more polluted cities, oxygen content in the air has been measured at 12 - 15%.
There are 297 words which start with 'pen'. 3 letter words starting with 'pen': pen. 4 letter words starting with 'pen': pend. pens.
Words that start with Tw. A list of words that start with Tw (words with the prefix Tw). We search a large scrabble dictionary for scrabble words starting with tw - we take the letter or word you enter, and generate all words starting with Tw. In addition there is a list of Words that end with tw, words that contain tw.