- MA plot
- MADS-box
- MAF
- MAFA
- MAFB
- MAFF
- MALAT1
- MALBAC
- MALT
- MALT lymphoma
- MAP kinase kinase kinase
- MAP2K4
- MAP3K1
- MAP3K7
- MAPK phosphatase
- MAPK1
- MAPK10
- MAPK11
- MAPK14
- MAPK15
- MAPK3
- MAPK8
- MAPKAPK2
- MAPKK
- MARK3
- MARK4
- MASP1
- MASP2
- MASS syndrome
- MBD1
- MBD3
- MBL deficiency
- MC1R
- MC3T3
- MCF-7
- MCHC
- MCM6
- MCPA
- MCV
- MCherry
- MD
- MDA-MB-453
- MDA-MB-468
- MDA5
- MDAT
- MDEA
- MDMA
- MDMA-assisted psychotherapy
- MDPV
- MDS
- MDia1
- MECP2
- MECP2 duplication syndrome
- MED1
- MEF2
- MEF2B
- MEF2C
- MEF2D
- MEG3
- MEG8
- MEGA
- MEIS1
- MEK
- MELAS syndrome
- MELISA
- MELK
- MEN1
- MEOX2
- MERCI Retriever
- MERRF syndrome
- MERS
- MERTK
- MESP2
- METAP2
- MF59
- MG132
- MHC
- MHC class I
- MHC class II
- MHC class III
- MHC restriction
- MHealth
- MIA PaCa-2
- MIBE
- MIBG
- MIDCAB
- MIMIC
- MIND diet
- MITF
- MIXL1
- MK-2206
- MK-434
- MLL
- MLL2
- MLL3
- MMEJ
- MMP1
- MMP11
- MMP14
- MMP15