1. Nearest in space or position; immediately adjoining without intervening space
   "our rooms were side by side"
   - adjacent, next 
2. Closely related or associated
   "a city in which communism and democracy had to live side by side"

See also: close, related, related to

• family Isuridae
• family Ixodidae
• family Jassidae
• family jewels
• family Juglandaceae
• family Juncaceae
• family Juncaginaceae
• family Jungermanniaceae
• family Kalotermitidae
• family Kasuwonidae
• family Kinosternidae
• family Kyphosidae
• family Labiatae
• family Labridae
• family Lacertidae
• family Lactobacillaceae
• family Lactobacteriaceae
• family Lamiaceae
• family Laminariaceae
• family Lamnidae
• family Lampridae
• family Lampyridae
• family Laniidae
• family Lanthanotidae
• family Lardizabalaceae