The words ‘loggerhead’ and ‘loggerheads’ belong to the same part of speech (nouns) but have different meanings.
loggerhead
- A type of turtle with a large head.
- A shrike (a type of bird) with mainly grey feathers and black eyestripe (head’s stripe which encloses or seems to run through the eyes), wings, and tail.
- (old-fashioned) A foolish person.
loggerheads
It is usually used as a prepositional phrase: at loggerheads.
When you’re at loggerheads with someone, you strongly disagree with them or you’re in a violent dispute with them.
Examples:
- We don’t need to be at loggerheads with each other.
- Politicians do not hide their feelings when they’re at loggerheads with opponents.