- the hard durable wood of any oak; used especially for furniture and flooring
- An Oak is a tree or shrub in the genus Quercus (Latin "oak tree"), of which about 600 species exist on earth. "Oak" may also appear in the names of species in related genera, notably Lithocarpus.
- A tree that bears acorns as fruit, and typically has lobed deciduous leaves. Oaks are common in many north temperate forests and are an important source of hard and durable wood used chiefly in construction, furniture, and (formerly) shipbuilding
- a deciduous tree of the genus Quercus; has acorns and lobed leaves; "great oaks grow from little acorns"
- A smoky flavor or aroma characteristic of wine aged in barrels made from this wood