srd
SRD
Entangled: The character is ensnared. Being entangled impedes movement, but does not entirely prevent it unless the bonds are anchored to an immobile object or tethered by an opposing force. An entangled creature moves at half speed, cannot run or charge, and takes a –2 penalty on all attack rolls and a –4 penalty to Dexterity. An entangled character who attempts to cast a spell must make a Concentration check (DC 15 + the spell’s level) or lose the spell.
Open Game Content from the System Reference Document 3.5, used under the Open Game License 1.0a.