5. Flat-flatly

‘Flat’ is used both in the direct (‘very close to the surface of smth’) and figurative (‘completely’) meanings, cf.:

Direct meaning

Flat Then they lay flat again and fired.(Hemingway).

Flatly --------

Figurative meaning

‘You take me flat aback, Aunt Em.’ (Galsworthy).

It was said flatly. The tone final. (Cussler); to refuse flatly.

NOTE: As seen from the last example, ‘flatly’ often occurs with verbs of speech.

5. High-highly.

‘High’ is used both in the direct (local) and figurative meanings. ‘Highly’ occurs only in figurative meaning (‘to a high degree’, ‘very well’), cf.:

Direct meaning

High The barman put his hands high in the air. (Chandler). I sprang as high as I could. (Knowles).

Highly -----------

Figurative meaning

He aims high. (Longman). He’s risen high in the world. (Ib.).

The Great Hotel was modest, highly respectable.(Galsworthy). He was highly suspicious of strangers. (Close). He speaks very highly of the boy’s behaviour. (Longman); highly paid.(Ib.).

5. Near-nearly.

The semantic difference btw these adverbs is distinct enough: ‘near’ is used in the direct (local) meaning (‘close’), ‘nearly’ is an adverb of degree meaning ‘almost’. Besides, ‘near’ is inflected for degrees of comparison, cf.:

Near ‘They said it was near Surrey Docks…’ (Pritchett). ‘Good morning, sir,’ said the one nearest him.(Waugh).

Nearly That was nearly thirty years ago. (Bates). I nearly lost consciousness on the Triborough Bridge. (Cheever).

5. Pretty-prettily

The semantic difference btw these adverbs is clear enough. The former is an adverb of degree meaning ‘rather, fairly’, the latter is a qualitative adverb meaning ‘in a pleasing or charming way’, cf.:

Pretty ‘You’re really pretty sure of me, aren’t you, Leo?’ (Littell). She dances pretty well. (Close).

Prettily Mary dresses very prettily. (Close).

5. Sharp-sharply

In some uses of theirs these forms are interchangeable, in particular with the verb ‘turn (abruptly)’, e.g. The road turns sharp(ly) to the left. (Hornby). Cf. Also:

Sharp As the crossroads we turned sharp (to the) left. (Close).

Sharply A sound of laughter was heard – they turned sharply. (Christie).

The phrase ‘to look sharp’ has two meanings: 1) to be watchful, e.g. ‘Look sharp!’ and 2) to be in a hurry, e.g. You have to look sharp if you want to be on time. (Longman). But the phrase ‘to look sharply’ means only ‘to look attentively, intently’, e.g. …the doctor looked at him sharply. (Christie). ‘Sharply’ is also used with verbs of speech, e.g. ‘And she said sharply: ‘Go!’ (Caillou).

In the meaning of ‘exactly, precisely’ only ‘sharp’ is used: e.g. The meeting starts at 3 o’clock sharp: don’t be late.’ (Longman).