must

To be obliged or required by morality, law, or custom.

To be compelled, as by a physical necessity or requirement.

Used to express a command or admonition.

To be determined to; have as a fixed resolve.

Used to indicate inevitability or certainty.

Used to indicate logical probability or presumptive certainty.

To be required or obliged to go.

Something that is absolutely required or indispensable.

Musk.