Japanese grammar

What does ～とともに mean? Japanese grammar N3

～とともに means together with; along with; at the same time as.

Quick facts
Level (estimated, JLPT framework)	N3
Structure	N／Vる + とともに
Romaji	totomoni
Meaning	together with; along with; at the same time as

Forming it

Connection	N／Vる + とともに

Two meanings: (a) together with someone/something (accompanying); (b) as A changes, B changes along with it.

Meaning (a) ACCOMPANYING: 「家族とともに移住した」 = moved together with the family. More formal than 「と一緒に」.
Meaning (b) PARALLEL CHANGE: 「年を取るとともに体力が落ちる」 = as one ages, strength declines.
Meaning (b) is close to 「～につれて」; 「とともに」 is more formal and can also be used for events happening at the same time.
Besides the “together with” (accompanying) meaning, 「とともに」 also expresses two events changing IN PARALLEL with each other, usually with verbs of increase/decrease: 「気温が上がるとともに、湿度も上がる」 (as the temperature rises, the humidity rises too).

家族(かぞく)とともに海外(かいがい)へ移住(いじゅう)した。
I moved overseas together with my family.
年(とし)を取(と)るとともに、体力(たいりょく)が落(お)ちてきた。
As I have grown older, my strength has declined.
新(しん)製品(せいひん)の発売(はつばい)とともに、問(と)い合(あ)わせが急増(きゅうぞう)した。
Along with the new product launch, inquiries surged.

Meaning (a) is used with people/organizations; meaning (b) is used with nouns denoting change.
More formal than 「と一緒に」.

Wrong家族(かぞく)にともに移住(いじゅう)した。

Correct家族(かぞく)とともに移住(いじゅう)した。

The meaning “together with” uses とともに.
Wrong（友達(ともだち)に）今日(きょう)は君(きみ)とともに帰(かえ)ろう。

Let's go home together today.

Correct（友達(ともだち)に）今日(きょう)は君(きみ)と一緒(いっしょ)に帰(かえ)ろう。

「とともに」 is written language; casual conversation uses 「と一緒に」.
Wrong彼(かれ)が来(く)るとともに、パーティーが始(はじ)まりました。

Just as he arrived, the party started.

Correct彼(かれ)が来(く)ると同時(どうじ)に、パーティーが始(はじ)まりました。

When two events coincide at exactly the same moment, use 「と同時に」; 「とともに」 leans toward parallel/gradual change.