ETYM Latin accretio, from accrescere to increase. Related to Crescent, Increase, Accrue.
Accumulation; addition of parts to form a whole; growth, especially by addition from outside.
1. An increase by natural growth or addition; SYN. accumulation.
2. Something contributing to growth or increase

ETYM Latin adhaesio, from adhaerere: cf. French adhésion.
Tendency of one thing to adhere to another; stickiness.
The property of sticking together (as of glue and wood) or the joining of surfaces of different composition
Faithful support for a cause or political party or religion

The union of diverse things into one body or form or group; SYN. coalescency.

1. Increase by the addition of particles
2. A growing together; coalescence