Meaning of “tone” - Learner’s Dictionary

tone

noun uk us /təʊn/
SOUND QUALITY [ C, U ]

B2 the quality of a sound, especially of someone's voice:

I knew by her tone of voice that she was serious.
FEELING/STYLE [ U, no plural ]

the general feeling or style that something has:

Then the director arrived and the whole tone of the meeting changed.
TELEPHONE [ C ]

B2 an electronic sound made by a telephone:

a dialling tone/an engaged tone
COLOUR [ C ]

one of the many types of a particular colour

(Definition of “tone noun” from the Cambridge Learner’s Dictionary © Cambridge University Press)