Definition of "building-block" [building-block]

• One of the temporary supports or blocks on which a ship's keel rests while the ship is building. (noun)
• One of a set of blocks with which children imitate the construction of buildings. (noun)

The Century Dictionary (Public Domain)

• "Although Seasonal Affective Disorder, or SAD, is typically associated with the darkest, shortest days of winter, the waning daylight is already reducing the availability from the sun of vitamin D, a building-block of serotonin, the neurotransmitter linked to depression."
• "Now that they had some room, they dove into building with their generic Danish building-block sets."
• "He collected all sorts of trading cards, building-block sets, books, and comics."