with leaflets usually numbering/arranged:
leaflets=5 or more, radiating from 🍁︎ one point (✋︎ palmate);  fruit a large capsule   >   🌰︎ chestnut/buckeye genus Aesculus

OR they are NOT (they have leaflets=3 or more, arranged pinnate ), but with . . .
leaflets have different sizes and shapes   >   boxelder Acer negundo

OR they are NOT, but with . . .
leaflets have no petiolule (grow direct from leaf-stem);  leaflets=7-(9)-11;  leaf length=25-40 cm (10-16 in)   >   black ash Fraxinus nigra

OR they are NOT, but with . . .
leaflets are regularly toothed;  twigs=square with corky wings   >   blue ash Fraxinus quadrangulata

OR they are NOT, but with . . .
twigs and leaf stalks are hairy   >   red ash Fraxinus pennsylvanica

OR they are NOT, but with . . .
leaflet uppersurface and undersurface=green;  leaf scar shape=D   >   red ash variant green ash Fraxinus pennsylvanica
leaflets=5-(7)-9;  leaflet undersurface=whitish;  leaf scar shape=C   >   white ash Fraxinus americana

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plant terminology