Το γράμμα λάμδα (επίσης λάμβδα) (κεφαλαίο Λ, πεζό λ) είναι το ενδέκατο γράμμα του Ελληνικού αλφαβήτου.
Στο ελληνικό σύστημα αρίθμησης έχει αριθμητική αξία λ´ = 30.
Lambda (uppercase Λ, lowercase λ; Greek: Λάμβδα or Λάμδα, lamda or lamtha) is the 11th letter of the Greek alphabet. In the system of Greek numerals lambda has a value of 30. Lambda is related to the Phoenician letter Lamed . Letters in other alphabets that stemmed from lambda include the Roman L and the Cyrillic letter El (Л, л). The ancient grammarians and dramatists give evidence to the pronunciation as [laːbdaː] (λάβδα) in Classical Greek times. In Modern Greek the name of the letter, Λάμδα, is pronounced [lamða]; the spoken letter itself has the sound of [l] as with Latinate “L”.
In early Greek alphabets, the shape and orientation of lambda varied. Most variants consisted of two straight strokes, one longer than the other, connected at their ends. The angle might be in the upper left, lower left (“Western” alphabets), or top (“Eastern” alphabets). Other variants had a vertical line with a horizontal or sloped stroke running to the right. With the general adoption of the Ionic alphabet, Greek settled on an angle at the top; the Romans, borrowing from Western alphabets, put the angle at the lower left.