1. Vitally important
   - life-and-death

See also: crucial, important

• genus Myrmecophaga
• genus Myrmeleon
• genus Myroxylon
• genus Myrrhis
• genus Myrsine
• genus Myrtillocactus
• genus Myrtus
• genus Mysis
• genus Mytilus
• genus Myxine
• genus Myxinikela
• genus Myxocephalus
• genus Nabalus
• genus Naemorhedus
• genus Nageia
• genus Naias
• genus Naja
• genus Najas
• genus Nanomia
• genus Napaea
• genus Narcissus
• genus Narthecium
• genus Nasalis
• genus Nasturtium
• genus Nasua