Definitions

1. noun

a unit of time equal to 1 second

“The timer went off at the si mark, signaling the start of the next round.”

2. interjection

an expression used to indicate agreement, confirmation, or acknowledgement

“Si, I will be there at 5 pm.”

3. adverb

used to indicate that something is done at the same time as something else

“He was walking si with his friend down the street.”