Tan is a synonym of tg.

As nouns the difference between tg and tan

is that tg is temporary gentleman while tan is a yellowish-brown colour.

As adjectives the difference between tg and tan

is that tg is transgender while tan is of a yellowish-brown.

As a verb tan is

to change to a tan colour due to exposure to the sun.

As a numeral tan is

the second cardinal number two, formerly used in Celtic areas, especially Cumbria and parts of Yorkshire, for counting sheep, and stitches in knitting.See Wikipedia article on Yan Tan Tethera

As a proper noun Tan is

an English surname derived from the transliteration of various Asian surnames, particularly originating from China and Vietnam.

As an initialism TAN is

Total Acid Number, the measure of a lubricant's or crude oil's acidity.