coalesce

verb

• (of separate elements) To join into a single mass or whole.

  "The droplets coalesced into a puddle."

• (of a whole or a unit) To form from different pieces or elements.

  "The puddle coalesced from the droplets as they ran together."

• To bond pieces of metal into a continuous whole by liquefying parts of each piece, bringing the liquids into contact, and allowing the combined liquid to solidify.