と
と
particle
and, with, (quotation)
1.
and (connecting nouns)
Connects nouns in a complete list. りんごとみかん (apples and oranges). Unlike や, と implies a complete enumeration.
2.
with (accompaniment)
Indicates doing something together with someone. 友達と行く (go with a friend).
3.
quotation marker
Marks quoted speech or thoughts. 「はい」と言う (say 'yes'), いいと思う (think it's good).
4.
if/when (conditional)
Expresses a natural or inevitable consequence. 春になると暖かくなる (when spring comes, it gets warm).
5.
as (comparison/manner)
Shows how something appears or is named. 同じと思う (think it's the same).
と has many uses. For listing: と gives a complete list (A and B), while や gives an incomplete list (A and B, etc.). For accompaniment: と implies doing something together, while に can mean toward someone. The conditional と expresses natural/automatic results and cannot be used with requests or commands.