You often use “together” in daily conversation. You can translate it into many words in Japanese. The ways of using them are subtly different. I would like to learn the meanings and how to use them together.
Japanese people very often use “issyoni”/「一緒に（いっしょに）」as the meaning of “together”. This isn’t casual and formal. You can say it to various things such as materials, people and so on. You can use it in both spoken and written languages. So it’s used in many situations. I think there is no problem to stay in Japan if you know “issyoni”/「一緒に（いっしょに）」. I will introduce the example.
A:Would you like to have lunch together ?/昼食に一緒に行きませんか？
B:Yes, that’s great !/はい、いいですね！
This is a little stiff expression although you can translate “together” into “tomoni”/「共に（ともに）」. I think it’s often used as a written language. Japanese people sometimes use it by Email in business situations. You can use it for materials, people and so on. Japanese people rarely say it in daily life. I think you should try not to say it in daily conversation because it’s unnatural that “tomoni”/「共に（ともに）」is used as a spoken language. In my opinion you don’t have to know this word just if you travel to Japan. I will introduce the example.
I and they together opposed the Japanese government policy./私と彼らは共に日本政府の政策に反対した。
You can translate “together” into “awasete”/「合わせて（あわせて）」in Japanese if you use the verbs which mean putting more than 2 things together. I will introduce the example.
I mixed soy sauce and sweet sake together./醤油とみりんを混ぜ合わせた。
I can also show you other examples. You can translate “link together” into 「繋ぎ合わせる（つなぎあわせる）」, “tie together” into 「束ね合わせる（たばねあわせる）」and “sew together” into 「縫い合わせる（ぬいあわせる）」.
You can also translate “together” into “dojini”/「同時に（どうじに）」when you use it as the meaning time or timing is same. You can also use “issyoni”/「一緒に（いっしょに）」about time or timing. I will introduce the example.
Don’t speak all together because I can’t understand what you mean !/何言ってるかわからないから、皆同時に話さないで！
You can translate “together” into 「一緒に（いっしょに）」which is used for materials, people and so on in a broad sense and isn’t casual and formal. So you can use it in many situations. “tomoni”/「共に（ともに）」is a little stiff expression and Japanese people often use it as a written language. I don’t recommend you should use it in daily conversation because Japanese people rarely use it as a spoken language. You can translate “together” into “awasete”/「合わせて（あわせて）」when you use the verbs which mean putting multiple things together. You can translate “together” into “dojini”/「同時に（どうじに）」when you use it as the meaning time or timing is same.