Learner's definition of TREND
1 : a general direction of change : a way of behaving, proceeding, etc., that is developing and becoming more common
the downward/upward trend of the stock market
Digital technology is the latest/current trend in television.
Teachers are trying to reverse the general trend [=tendency] of lower test scores.
There is a disturbing/growing trend toward obesity in children.
trends in fashion
The director has set/started a (new) trend in moviemaking. [=other directors are copying the director's way of making movies]
2 : something that is currently popular or fashionable