The mathematical symbol of xiangru is the Greek letter λ, which is pronounced "Lambda". Greek alphabet is a letter used in Greek, and it is also widely used in mathematics, physics, biology, astronomy and other disciplines. Greek letters are similar to English letters and Russian letters, but with different symbols and the same phonetic properties.

Greek letters are the earliest letters with vowels in the world. Cyrillic letters and Georgian letters used in Russian and Ukrainian are all developed from Greek letters, so people who have studied Russian will feel deja vu when they use Greek letters. Greek letters have entered the vocabulary of many languages. For example, the international word Delta comes from the Greek letter δ, because δ is a triangle.

The Greek alphabet comes from the Phoenician alphabet, which has only consonants and is written from right to left. The internal Greek developed vowels, and the Greeks added vowels. Because the Greek writing tool was a wax board, sometimes the first line was written from right to left, and the second line was written from left to right, which became the so-called "cultivated land" writing. Later, Chengdu gradually evolved from left to right.