In plural. Those things belonging to or constituting the substance; the essential parts or elements; (the) essentials. Also occasionally in singular…

A faculty or quality of the mind or soul; (also) the inner nature or character of a person, etc.; the spirit.

A thing that is formal; esp. (originally and chiefly U.S.) (an) evening dress; an engagement at which such dress is worn.

A basic or primary principle, rule, law, or article, which serves as the groundwork of a system; an essential part. Chiefly in plural.

In plural. The constituent, intrinsic, or essential parts of something. Obsolete.

plural. Inmost nature; ‘vitals’. Obsolete. rare.

figurative. Something lacking in substance or appeal; basic or unpalatable (intellectual) fare. Also: the basics, the essentials.

The essential or elementary aspects of a situation, subject, etc.; fundamentals; primary requirements.

An underlying or basic principle; = fundamental, n. 1a.