1.  Delta is the fourth letter in the Greek alphabet.

2.  Delta is a voiced dental consonant. Its phoneme is formed with the tip of tongue behind the upper teeth. The vocal cords vibrate as the phoneme is uttered. You can test this by putting your fingers on your vocal cords and practice saying the phoneme.

3.  Delta's upper and lower case letters look very dissimilar from each other. Both letters are formed by one stroke without lifting the pen from the paper.

4.  Delta is transliterated into English as "D" or "d."