This is the 548th most frequent Japanese word.
通信
Communication; correspondence; transmission.
In this sentence, "通信" refers to communication technologies or systems studied as a discipline.
彼は大学で通信工学を学んでいる。
He is studying communication engineering at university.
Here, "通信" is used to describe data transmission over the internet.
インターネット通信が遅いため、ファイルのダウンロードに時間がかかる。
The internet communication is slow, so downloading the file takes time.
In this example, "通信" denotes the act of communicating through electronic correspondence.