Fundamental and maximum frequency of a signal!

Hello

I understand the following question is very silly, however I am not sure about the answer.
Lets consider we are saying there is a signal with a frequency of 4 Hz (for example). In such a statement, does it mean the maximum frequency is 4 Hz for this signal? If it does, why we refer it as the maximum frequency? What are other frequencies of this signal then? Or, should we say the max frequency is 4 Hz and the min frequency is 0 Hz for this signal, hence the baseband bandwidth is equal to 4 Hz if it is considered as a baseband signal.

In addition, what would be the fundamental frequency (the lowest frequency component based on what the harmonics are determined) of such signal if we say a signal exists with frequency of 4 Hz?
So, how do you identify the fundamental frequency and the maximum frequency?

I would appreciate your time answering this.

saying there is a signal with a frequency of 4 HZ exactily means a tone signal which frequency is 4 HZ.
Usually we say a signal with x HZ bandwidth. The bandwidth equals to highest frequency minus lowest frequency.

Yes, I agree with naturemalett.
It is uncomplete simply to say "signal with 4 Hz". In order to avoid misunderstandings it is necessary to add for example "sinusoidal" or "squarewave repetition rate" or something similar.

Pure sine wave has exactly one frequency. But, in real world there is no such thing as pure sine. We cannot generate a pure sine wave and every oscillator wil generate a sine wave with a phase noise, which is equivalent to a band of frequencies about the center frequency.

Waveforms have a spectrum in frequency domain which determines the power contribution of each frequency. and as naturemallet said "The bandwidth equals to highest frequency minus lowest frequency."