Onset or outset: Which is which?

[Michael E. Galario]

Hi Sir Joe,

Could you please explain the semantic difference between  onset and outset and how to use them correctly in a sentence. Also, can these be used interchangeably?

Thank you.

[Joe Carillo]

The nouns “onset” and “outset” mean the same thing, which is “beginning,” “start,” or “commencement,” but their usage and syntax differ so they can’t be used interchangeably. We say “Inspection of the city's drainage canals were done at the onset of the rainy season” but not “Inspection of the city's drainage canals were done at the outset of the rainy season.” On the other hand, we say “We told you at the outset that she will surely lose” but not “We told you at the onset that she will surely lose.”

[Michael E. Galario]

By your explanation sir Joe, it gives me an impression that "outset"has a meaning that something would be happening or would be unfolded in a discussion while "onset" gives me an impression that something happens in the beginning and ends there. The action/motion is quantified during the said period. Outset, on the other hand, seems it forewarns or foretells what possible things a reader or listener can expect from someone's argument/statement. It's like it carries an idea of action/motion.

[Joe Carillo]

I find that the meanings you discerned from the words "onset" and "outset" are not reflected in authoritative English dictionaries. Both are just shades of meaning of the nouns “beginning,” “start,” and “commencement” and none intrinsically carries the additional senses you described. It's in their actual usage--meaning how they are combined with other words--that they evoke particular senses or impressions. To avoid wrong semantics, I think it's advisable that we leave the matter at that.