Ja; Well Then.

Japanese people use “Ja” quite often.

“Ja” is another magic word which can be used almost anything.

It’s just like “Well” in English.

“Ja” is “Good bye”.
“Ja” is “See you”.
“Ja” is “Yes”.
“Ja” is “No”.“
Ja” is “Then”

Japanese people love to shorten sentences. They don’t finish the sentence. The listeners must guess from both the situation, tone of the voice, and the facial expression.

It is strongly connected with Japanese mind (which I must tell you at some point in the future).

Ja. 
A little word.
A small word.
Meaning big.
Meaning a lot.