Grammatical structure in “best avoided”

I come across some phrases such as “best avoided,” or “better avoided.” I understand what it means, but don’t know how this phrase was made. What grammatical structure is in this? I thought this phrase is short for “is best (when it is) avoided,” but this underatanding is just based on my rudimentary grammar. Could anyone help me with this?

Solution 1:

In your case 'best' is an adverb form which is used to modify a verb.

Here's an extract from the entry in Merriam-Webster's Dictionary (https://www.merriam-webster.com/dictionary/best):

best

superlative of WELL

1: in the best way 

: to greatest advantage

// Some things are best left unsaid.

The same thing is with 'better':

better

comparative of WELL

1a: in a more excellent manner // sings better than I do

b: to greater advantage  :PREFERABLY // some things are better left unsaid

(https://www.merriam-webster.com/dictionary/better)