How do you pronounce the word cetaceans?

Answer 1

cetaceans can be pronounced: set aye sh'ns

there is a slight emphasis on the second syllable

I have indicated the use of a weak vowel (technically a shwa) in the last syllable, by using an apostrophe. I hope this makes sense to you.

Answer 2

The name for the marine mammals is pronounced (seh-TAY-shunz) or (sih-TAY-shunz). The first and third syllables are unstressed, the first eh or ih and the third a schwa.