an-ti-ci-pa-tion
n.
1. The act of anticipating.
2. An expectation.
3. Foreknowledge, intuition, and presentiment.

ap-pre-hen-sion
n.
1. Fearful or uneasy anticipation or the future; dread.

re-ac-tion
n.
1. A response to a stimulus.
2. The state resulting from such a response.

ap-per-cep-tion
n.
1. Conscious perception with full awareness.
2. The process of understanding by which newly observed qualities of an object are related to past experience.

ac-cep-tance
n.
1. The act or process of accepting.
2. The state of being accepted or acceptable.

e-vo-lu-tion
n.
1. A gradual process in which something changes into a different and usually more complex or better form.