Русско-английский научно-технический словарь
см. тж. совершенно необходим; требоваться
• Cobalt is required in small amounts by plants and animals.
• In science, as opposed to pure philosophy, observable facts are requisite.
• To attain the high performance, powerful turbojets, rockets, or ramjets became a necessity.
• It takes at least a minute for the chamber to come to equilibrium.
• New approaches are called for.