Parsley is a bright green biennial herb, often used as spice. It is common in Middle Eastern, European, and American cooking. In modern cooking, parsley is used for its leaf in much the same way as coriander (which is also known as Chinese parsley or cilantro), although parsley is perceived to have a milder flavor.
It is a fungus.
Stem of mustard plant is green and tender so it is a herb
Lemon is neither an herb nor a shrub. It is a tree.
shrub
shrub
Shrubs
tree
Tree
A cucumber is a fruit (it contains seeds) but can also be classified as a vegetable.
A bougainvillea is a shrub or small tree.
Technically it is called a herbaceous shrub
Lemon plant is a tree, where the lemon fruits are growing. Those lemons, what we buy in grocery stores.