1. (adjective) fit or ready for use or service

• functional
• operable
• usable
• useable

2. (adjective) being in effect or operation

• in operation
• operating

1. (adjective) fit or ready for use or service

• serviceable

2. (adjective) (military) of or intended for or involved in military operations

• active
• combat-ready
• fighting
• effective

3. (adjective) being in effect or operation

• operative

1. (adjective) (military) of or intended for or involved in military operations

• armed forces
• armed services
• military
• military machine
• war machine

1. (adjective) fit or ready for use or service

• apply
• apply
• employ
• employ
• use
• use
• utilise
• utilise
• utilize
• utilize
• functionality
• serviceability
• serviceability
• serviceableness
• serviceableness
• usability
• usability
• usableness
• usableness
• useableness
• useableness

1. (adjective) (military) of or intended for or involved in military operations

• inactive
• nonoperational

1. (adjective) pertaining to a process or series of actions for achieving a result

• operation
• procedure