Heed, attend to
Assister means 'to attend' (a class, a conference, ..), or 'to help' (to be of assistance, which has the same roots).
absent
A word that has the same meaning as another word is a synonym.
Another word meaning clenched is tighten.
The meaning of a word is its "definition."
"It was doubtless they would have to attend the class."
cherish, accomplish, and attend
A synonym is a word with a meaning similar to that of another word.
The smallest class of sound that makes a difference in meaning is called a phoneme. Phonemes are the basic units of sound that distinguish one word from another in a particular language. Changing a phoneme can result in a change in meaning.
Another word meaning "to influence" is "affect" or "impact."
participated, took part of