Linctus is a type of syrupy medicine that is used to treat coughs and other respiratory illnesses. It is usually composed of an expectorant, such as ammonium chloride, and a sweetener, such as sugar or honey. It is often prescribed for children and the elderly, as it is easier to swallow than solid tablets. Linctus is also known as a 'cough syrup' and is available in both over-the-counter and prescription forms.