above / over
Two prepositions of place, amount, and rank.
Above and over overlap, and either will often do. Prefer above for a position higher than something else with space between, and for rank or a figure on a scale: above the clouds, above average, the office above mine. Prefer over for covering, crossing, authority, or motion across: a blanket over the child, a bridge over the river, over the limit, power over the committee. Do not invent a ban on one word where ordinary English uses both.
Examples
UseThe painting hangs above the fireplace.
UseFog settled over the valley.
UseTemperatures rose above ninety.
PreferShe has authority over the budget.
Over is the usual choice with all in the sense “more than” (over two hundred pages). Above remains natural with average, zero, and similar benchmarks.