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a∅∅ annihilates concatenation: a∅ = ∅ConcatenationFormal RE✨ Emoji Combos

If any component of a concatenation is ∅, the whole expression is ∅. There is no string in L(∅) = {} to concatenate.

✓ Accepts
nothing — L = ∅
✗ Rejects
aabanything
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