Why should I use "a" before "a bit better", "a littlge highter" "a bit harsh"?

Question

in this phrase(I am not sure this is a phrase)but

Why should I use "a" before

"a bit better", "a little higher" and "a bit harsh"?

I know this is an article( a or the) and I know why I need to use a or the before such as an apple, the school, a store but I do not know why I need to use a before these phrases.. In my opinion, it still makes sense to me even though I say "Sundays were bit better" something like that(even grammarly says I need to use "a", but I do not know why..

Can someone explain to me? Thank you in advance

Answer 1

In your examples "a bit" means somewhat; to some extent. [Lexico] Although it's short, it is a set phrase: you would need to ask an etymologist why it starts with "a".

"a little" - in your examples - means "slightly". You need "a" because without it the meaning changes completely.

For example. You ask your partner to move a bookshelf a few inches higher. When s/he has finished you go and look at it.

If it is a little higher than it was you may be pleased.
If it is little higher than it was you may be disappointed.

Answer 2

A bit and a little need the article because they are nouns meaning a small amount. If something is a bit better it is better by a small amount. Slightly, much and other adverbs you might use do not need an article.