This is the 22nd most frequent Japanese word.
会
"会" means "meeting," "gathering," or "association."
In this sentence, '会' is part of '会議', which means 'meeting' or 'conference', representing an event happening where people gather.
彼は会議に行った。
He went to the meeting.
Here, '会' is used in '同窓会', referring to a gathering or meeting, in this case, of alumni.
来週の同窓会に参加します。
I will attend the alumni gathering next week.
Here, '会' is part of the verb '会う', which means 'to meet', showing the act of meeting another person.