It's very small. Unassuming, you might say. And can be found inside the word 'unassuming' and also inside 'assuming'.
What a complicated way to reach the word itself! Namely: 'as'.
What has 'as' done to deserve my hostility?
Nothing much. It's not rational. Each of us develops different bees in different bonnets — as it were.
And I don't say I never use it (I just did). But I can't choose it without caution.
For me, the first issue is that although 'as' is so small, it has at least three or four meanings. (Merriam Webster has nine entries!)
Each possible meaning has a different effect on the line. It can be hard sometimes to see which of them is intended.
The worst of the possible meanings of 'as' (in my book) is 'because'. When it means 'because', it sounds like a phrase book for someone learning to speak English.
For example, 'I ate every scrap of my dinner as I was ravenous'.
Or 'As the bus was full, I caught the train.'
'As' used in this way deadens a sentence. Nobody would ever say, 'I ate my dinner as I was hungry.' It's better to split the sentence into two, or use a dash: 'I wolfed my sandwich — I was ravenous.'
(I don't like the sound of 'as' either. The 's' sounds as 'z'. It reminds me of the word 'gristle', and gristle reminds me of cheap sausages.)
When 'as' means 'because', it functions as a connective, or conjunction. But even when 'as' connects two clauses, it can have more than one meaning, the other most likely possibility being 'while'.
'As I combed my hair, I thought of my mother', for example. Or: 'The surf glistened as the moon rose high above the waves.'
The third meaning is the one I least dislike. As fast as lightning. As white as milk. When used in a simile,'as' often pops up twice (once on each side of the adverb) and I don't mind this in the least. However, it means the number of usages quickly multiplies:
As the moon rose into the sky,
the boat slipped over the horizon
as fast as night. It was a slow boat,
a cold boat. As it had no sails,
so no sailors and no oars.
As it vanished, it left no sign.
As if it had never ever been.
'As' is so small — so unassuming — its repetitions slip past the most eagle-ish of eyes.
But it can damage sharpness of phrase. It can smudge clarity and precision.
I hate 'as'.
As I said earlier, it's not rational.