[awk-sin] 
| a class of substances that in minute amounts regulate or modify the growth of plants, esp. root formation, bud growth, and fruit and leaf drop. |
| aux·in (ôk'sĭn) n. Any of several plant hormones that regulate various functions, including cell elongation. [From Greek auxein, to grow; see aug- in Indo-European roots.] aux·in'ic adj., aux·in'i·cal·ly adv. |
sɪn