all four pairs are turning

three pairs turning and one pair sliding

two pairs turning and two pairs sliding

one pair turning and three pairs sliding

bevel gear

universal joint

Hooke's joint

Knuckle joint

Thompson indicator

Richard indicator

Simplex indicator

Thomson indicator

the former is mathematically accurate

the former is having turning pair

the former is most economical

the former is most rigid

compound gears

worm and wheel method

Hooke's joint

crown gear