pentad /penˈtad/

1. A set of five things
2. A period of five years or five days
3. An atom, element or radical with a combining power of five

pentadˈic adjective

• backwardly
• backwardness
• backwardnesses
• backwards
• backwards-compatible
• backwash
• backwashed
• backwashes
• backwashing
• back water
• backwater
• backwaters
• backwoods
• backwoodsman
• backwoodsmen
• backword
• backwords
• backwork
• backworker
• backworkers
• backworks
• back-wounding
• backyard
• backyards
• baclava