Some Common Look-Alikes you may encounter

Box Elder

Exhibits opposite branching and compound leaves.
However, has 3 to 5 leaflets (instead of 5 to 11) and the
samaras are always in pairs instead of single like the ash.

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Elm

Branching is alternate and the leaves are simple with an
unequal leaf base.

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Basswood (American Linden)

Bark similar to Ash, but branching is alternate and leaves are simple, very large, and roundish