connective N4 common casualpolitewritten

と一緒に — together with

と一緒にといっしょに

Meaning

together with ~ / along with ~ — does the action jointly with the named person or thing

友ともだちと一緒いっしょに映画えいがを見みた。

I watched a movie together with a friend.

Attaches to	Form	Example
Noun と + 一緒いっしょに	N と一緒いっしょに	家族かぞくと一緒いっしょに (together with my family)

牛乳ぎゅうにゅうと一緒いっしょに薬くすりを飲のむ。

Take the medicine together with milk.

みんなと一緒いっしょに歌うたいましょう。

Let's all sing together.

The opposite is 一人ひとりで ('alone / by oneself'). 一緒いっしょに can also stand without a partner noun to mean simply 'together' (一緒いっしょに行いこう = 'let's go together').

Jengo shows と一緒に the way you actually meet it: inside real Japanese sentences, so it sticks instead of staying an abstract rule.

Sources Compiled with reference to A Dictionary of Intermediate Japanese Grammar.