Fix, Mend, Repair
Fix means to make fast, but its incorrect use in the sense of mend, repair, arrange, is so common that the word when properly used sounds strange, if not strained. “To fix up the room,” “to fix up the accounts,” “to fix up matters with my creditors,” “to fix the rascals who betrayed me,” are examples illustrating the looseness with which the word is used.
Round, Square
When a thing is round or square it cannot be rounder or squarer. These adjectives do not admit of comparative and superlative forms. But we may say more nearly round or less nearly square.
States, Says
“He states he is going fishing to-morrow.” States is too formal a word, and should be used only of some important assertion. “He says he is going,” etc.
Stop, Stay
To stop is to cease moving. “At what hotel do you stop” should be “At what hotel do you stay.” “When you come to the city stay with me,” not stop with me.
Subtile, Subtle
Subtile means thin, fine, rare, delicate; subtle means sly, artful, cunning, elusive. “More subtile web Arachne cannot spin.” “He had to contend with a subtle foe.”