interstice /in-tûrˈstis/

1. A small space between things closely set, or between the parts which compose a body
2. The time interval required by canon law before receiving higher orders (RC)
3. A space between atoms in a lattice where other atoms can be located

interstitial /-stishˈl/ adjective

1. Occurring in an interstice or interstices
2. Containing interstitial atoms or ions (chem)
3. Relating to the surfaces of teeth where they adjoin (dentistry)

An extra atom in a crystal lattice, causing a defect

interstitˈially adverb

• trade gaps
• trade in
• trade-in
• trade-ins
• trade journal
• trade journals
• trade-last
• trade-lasts
• tradeless
• trade mark
• trademark
• trade marked
• trademarked
• trade marking
• trademarking
• unbundles
• unbundling
• unbundlings
• unburden
• unburdened
• unburdening
• unburdens
• unburied
• unburies
• unburned