A clerical collar, clergy collar, or, informally, dog collar, is an item of Christian clerical clothing.
Church of Sweden Lutheran priest Sven-Erik Brodd [sv] wearing a clerical shirt with a "tab collar".
An Anglican military chaplain wearing a "dog collar" (full collar) during World War I
A plastic clerical collar
Jacques Habert, Roman Catholic bishop of Bayeux
Clerical clothing is non-liturgical clothing worn exclusively by clergy. It is distinct from vestments in that it is not reserved specifically for use in the liturgy. Practices vary: clerical clothing is sometimes worn under vestments, and sometimes as the everyday clothing or street wear of a priest, minister, or other clergy member. In some cases, it can be similar or identical to the habit of a monk or nun.
On the right, an example of the full collared shirt and cassock; on the left, a clerical shirt that could have a tab collar inserted.
The rabat, worn until the early 20th century.
Anglican cassock, rochet, chimere and scarf.
The ruff, as worn by a Danish Lutheran bishop.