The difference between Dawn and Onset

When used as nouns, dawn means the morning twilight period immediately before sunrise, whereas onset means a rushing or setting upon.

When used as verbs, dawn means to begin to brighten with daylight, whereas onset means to assault.

check bellow for the other definitions of Dawn and Onset

Dawn as a verb (intransitive):

To begin to brighten with daylight.

Examples:

"A new day dawns."
Dawn as a verb (intransitive):

To start to appear or be realized.

Examples:

"I don’t want to be there when the truth dawns on him."
Dawn as a verb (intransitive):

To begin to give promise; to begin to appear or to expand.

Dawn as a noun (uncountable):

The morning twilight period immediately before sunrise.
Dawn as a noun (countable):

The rising of the sun.
Dawn as a noun (uncountable):

The time when the sun rises.

Examples:

"She rose before dawn to meet the train."
Dawn as a noun (uncountable):

The beginning.

Examples:

"the dawn of civilization"

Onset as a noun (archaic):

A rushing or setting upon; an attack; an assault; a storming; especially, the assault of an army.
Onset as a noun (medicine):

The initial phase of a disease or condition, in which symptoms first become apparent.

Examples:

"the onset of schizophrenia"
Onset as a noun (phonology):

The initial portion of a syllable, preceding the syllable nucleus.

Examples:

"ant coda"

"coordinate terms nucleus coda"

"holonyms syllable"
Onset as a noun (acoustics):

The beginning of a musical note or other sound, in which the amplitude rises from zero to an initial peak.
Onset as a noun:

A setting about; a beginning.

Examples:

"synonyms: start beginning Thesaurus:beginning"

"the onset of puberty"
Onset as a noun (obsolete):

Anything set on, or added, as an ornament or as a useful appendage.

Examples:

"rfquotek Johnson"