"emit" keyword optional when calling signals?

Is using the "emit" keyword before a signal function necessary? I forgot to add it so some cases when I call a signal, but they still seem to work.
e.g.

Code:

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mySignal();

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instead of

Code:

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emit mySignal();

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I was wondering if there is any difference if I leave it out?

emit is an empty macro but you should use it to increase readability.