Difference between flexion and contraction?
Flexion: the movement that decreases the angle between two parts [1]. Examples: clenching the hand into fist, sitting down.

Contraction: the property of muscle to generate tension when actin and myosin filaments are crossing. There are a few types of contractions. The isometric contraction is when the muscle generates tension but its length doesn't change (for example when you try to lift something that you can't). The isotonic contraction is when the muscle changes its length [2]. This kind of contraction leads to movements and can lead to flexion too.



References:


Wikipedia contributors, "Anatomical terms of motion," Wikipedia, The Free Encyclopedia, http://en.wikipedia.org/w/index.php?title=Anatomical_terms_of_motion&amp;oldid=612679254 (accessed June 26, 2014).
Wikipedia contributors, "Muscle contraction," Wikipedia, The Free Encyclopedia, http://en.wikipedia.org/w/index.php?title=Muscle_contraction&amp;oldid=609265714 (accessed June 26, 2014).