(ergative) To sign up to have copies of a publication, such as a newspaper or a magazine, delivered for a period of time.

To pay for the provision of a service, such as Internet access or a cell phone plan.

(used with to) To believe or agree with a theory or an idea .

To pay money to be a member of an organization.

(intransitive) To contribute or promise to contribute money to a common fund.

(transitive) To promise to give, by writing one's name with the amount.

(business and finance) To agree to buy shares in a company.

(transitive) To sign; to mark with one's signature as a token of consent or attestation.

(archaic) To write (one’s name) at the bottom of a document; to sign (one's name).

(obsolete) To sign away; to yield; to surrender.

(obsolete) To yield; to admit to being inferior or in the wrong.

(obsolete, transitive) To declare over one's signature; to publish.

(intransitive) To indicate interest in the communications made by a person or organization.

(intransitive, programming) To register for notifications about an event or similar.