Wikipedia:Link to what it is

On Wikipedia the lead of every article should contain links to what the topic of the article is. The article about chairs should link to "furniture" and "seat" in the lead because a chair is a piece of furniture used as a seat.

Thus: "Diamond is a solid form of the element carbon with its atoms arranged in a crystal structure called diamond cubic."

is preferable to: "❌ Diamond is a solid form of the element carbon with its atoms arranged in a crystal structure called diamond cubic."

This makes articles more accessible to readers by allowing them to click a link to a term they are not familiar with rather than doing a search for that term. This, in turn, reduces the demand for definitions and assists with Wikipedia not being a dictionary.

Often the terms used in the article title should each be linked to upon their second statement in the lead of the article. Thus "Pearly gates" should link to both "gate" and "pearl" (as well as "heaven", where the gates lead).