My 2-year-old lovebird has very weak legs. He cannot stand and he holds himself with his head and balances with his
I have a peach-faced lovebird. His beak was the usual bone or cream color, but now it has changed. The entire beak is affected, especially at the top where it connects to his face. This change occurred rapidly; we noticed it just two days ago. No other changes have been observed.
I mean here "You are the best at tennis" "and "you are best at tennis", "choose the book you like the best or best" both of them can have different meanings but "most" and another adverb in a standalone sentence has a completely different meaning.
Both sentences could mean the same thing, however I like you best. I like chocolate best, better than anything else can be used when what one is choosing from is not specified I like you the best. Between chocolate, vanilla, and strawberry, I like vanilla the best can be used when choosing from some choices.
In your context, the best relates to {something}, whereas best relates to a course of action. Plastic, wood, or metal container? What was the best choice for this purpose? Plastic, wood, or metal container? What was best to choose for this purpose? Either is acceptable, and the practical meaning is the same, but their referents, implicit not explicit, are different.
The word "best" is an adjective, and adjectives do not take articles by themselves. Because the noun car is modified by the superlative adjective best, and because this makes the noun car definite in this context, we use the. It is best not to do something. Here, we have the adjective best, but this adjective is attached to no noun.