building_block
1. [ noun ] a single undivided natural entity occurring in the composition of something else
Synonyms: unit
Examples:

"units of nucleic acids"

Related terms: entity thing group molecule chain unit_cell couple part unitize
2. [ noun ] (architecture) a block of material used in construction work
Related terms: building_material cinder_block voussoir keystone ashlar
Similar spelling:   building_society
  building_site
  building_code
  building_material
  building_permit
  building_complex