Tis is a short way for writing "It is"

A form of autism

Middle English/Early Modern English contraction of "it is".

The mysterious and poorly-defined zone of flesh marking the transition between the penis and the balls. Contrary to the more exclusive taint, 'tis, at the same time, both your dick and your balls.

To answer in the affirmative

A conjunction used instead of saying it is or it's.
the word was the most popular in the medi-evil era,

commonly in shakespearian play
but is used modernlys as well.

The Danish word for pee (urine).