Selenium and Se

Selenium noun - A toxic nonmetallic element related to sulfur and tellurium; occurs in several allotropic forms; a stable grey metallike allotrope conducts electricity better in the light than in the dark and is used in photocells; occurs in sulfide ores (as pyrite).

Se and selenium are semantically related. In some cases you can use "Se" instead a noun "Selenium".

Se noun - A toxic nonmetallic element related to sulfur and tellurium; occurs in several allotropic forms; a stable grey metallike allotrope conducts electricity better in the light than in the dark and is used in photocells; occurs in sulfide ores (as pyrite).

Selenium and Se are semantically related. You can use "Selenium" instead a noun "Se".