1A conjunctive particle used to list or add facts and qualities — 'and (what's more)', 'besides', 'not only ... but also'. Often used as 〜し、〜し to pile up several points.
この店は安いし、味もいい。
This place is cheap, and the food's good too.
彼女は優しいし、頭もいい。
She's kind, and smart too.
部屋は広いし、駅にも近い。
The room is spacious, and it's close to the station.
今日は天気もいいし、散歩に行こう。
The weather's nice today, so let's go for a walk.
2A conjunctive particle giving one of several reasons ('because', 'since'); it typically introduces a reason, with a judgment or conclusion following.
今日は疲れているし、早く帰るよ。
I'm tired today, so I'll head home early.
もう遅いし、そろそろ失礼します。
It's late, so I'll be going soon.
雨も降っているし、出かけるのはやめよう。
It's raining too, so let's not go out.
3Used at the end of a sentence to state just a reason and leave the conclusion unsaid, trailing off; often carries a nuance of excuse, complaint, or hesitation.
行きたくないなあ。寒いし。
I don't really want to go. It's cold, and all...
まあいいか。もう終わったことだし。
Oh well. It's over and done with anyway.
別にいいよ、暇だし。
Sure, it's fine — I'm free anyway.