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this; this one
this person
now; this point (in time)
used to stress the subject of a sentence
「是」 has another reading with different meanings.
righteousness; justice; right
是ぜひ非来きてくださいね。
Please do come.
今日きょうは是ぜひ非参加さんかしたいと思いおもいます。
I definitely want to join today.
是ぜひ非お願いねがいしたいだった。
I really want to ask you.