Worry

A cognitive process involved in the experience of anxiety that serves to maintain high levels of vigilance for personal danger. Compared with anxiety, worry is more closely associated with problem-solving (confidence, approach rather than avoidance of a problem and personal control of the problem). Worry is also less associated with negative affect (e.g. depression, confusion) compared with anxiety.

Reference:
Mathews, A. (1990). Why worry? The cognitive function of anxiety. Behaviour Research and Therapy, 28(6), 455-468. doi: 10.1016/0005-7967(90)90132-3

Zebb, B. J., & Beck, J. G. (1998). Worry Versus Anxiety Is There Really a Difference?. Behavior Modification, 22(1), 45-61. doi: 10.1177/01454455980221003