noun
A sign, gesture, sound, or device that conveys information or instructions. Used in both technical and everyday contexts.
赤は止まれのシグナルだ。
Red is a signal to stop.
彼は手でシグナルを送った。
He sent a signal with his hand.
信号 is the native Japanese word for 'signal', often used for traffic lights and formal contexts, while シグナル is a loanword with a slightly more modern or technical feel.
Borrowed from English 'signal'.