a line of approach
"they explored every avenue they could think of"
"it promises to open new avenues to understanding"
A broad street, especially one bordered by trees.
"We took a leisurely walk down the tree-lined avenue to enjoy the cool shade on such a hot day."
In plain English: An avenue is a wide street with trees on both sides that people drive or walk down.
"The new shopping center is located on the main avenue."
Usage: Use "avenue" to describe a wide, often tree-lined public road that typically runs at right angles to other streets. Avoid using it to mean a plan or method, as that requires the word "avenue" in a metaphorical sense rather than its primary physical definition.
The word "avenue" was borrowed from the French avenue, which originally meant an approach or arrival. It traveled into English to describe a road that leads somewhere, rather than just retaining its literal sense of coming to a place.