Practise the thinking. Keep the judgement.
一緒に (issho ni): Together; with someone
いっしょに
issho ni
Meaning
Together; with someone
Two original examples
友だちと一緒に昼ご飯を食べます。
I eat lunch together with my friend.
一緒に帰りませんか。
Shall we go home together?
Usage and distinctions
一緒 is the noun/adjectival base, while 一緒に modifies an action. The small っ represents a short stop in pronunciation. と identifies the companion: 友だちと一緒に. 一生（いっしょう, a lifetime）is a different word.