- littermates
- labelled protein
- look for trouble
- lip service
- lipservice
- logic function
- logician
- look sharp
- lobelia nicotianiae folia
- looking pretty
- luer syringe
- lingustrum lucidum
- larngismus paralyticus
- lecithinosis
- lambdoid suture
- lutheran gene
- louping
- logarithmic ratio
- lit. to 'play with mud marbles'—to act in an inexperienced manner
- lactobacillus bulgaricus
- librarianship
- light beam diaphragm
- locumtenens
- laparoscope
- lit. '(my) father was a monarch'—to harp on one's royal past
- low(er) cast
- line control block
- luteotrophin
- luteotropic
- lust after
- load the dice
- luteolin
- leucocidin
- larrup
- leucopheresis
- leuconostoc mesenteroides
- leucotome
- leucotaxine
- leukoagglutinin
- lattice structure
- lung to tongue time
- latticed fibre
- lattice like
- lattice plane
- lattice degeneration
- limpet
- lobbyist
- limbless
- lascivious
- licentious