Q: Are “wood” and “wooden” interchangeable?
A: The words “wood” and “wooden” can sometimes be used for each other, but we wouldn’t describe them as interchangeable.
When used adjectivally to describe something made out of the material from a tree, “wood” and “wooden” mean the same thing (as in “wood shutters” or “wooden shutters”).
But when used figuratively to describe something stiff, awkward, unnatural, or emotionless, only “wooden” will do (“wooden expression,” “wooden performance”).
Even when “wood” and “wooden” mean the same thing, we wouldn’t necessarily consider them interchangeable. The choice of one or the other often depends on rhythm, style, euphony, and so on.
If they were switched in these two passages, the iambic meter would be disrupted:
“Upon a wooden coffin we attend” (from Shakespeare’s King Henry VI, Part 1, believed written in 1591).
“the very sap of their wood-fewel burning on the fire” (from Milton’s Moscovia, an early work published posthumously in 1682).
Technically, “wooden” is an adjective while “wood” here is a noun used attributively—that is as an adjective. When a noun like “wood” is used adjectivally, it’s often referred to as an attributive noun, a noun adjunct, or a noun premodifier.
In general, adjectives are more flexible than attributive nouns. You can use an adjective as a simple premodifier (“blue scarf”), with an adverb like “too” or “very” (“a very blue scarf”), and as a comparative or superlative (“a bluer scarf”).
You can also use an attributive noun as a premodifier (“a wool pullover”), but it’s unidiomatic to use it with “too” or “very” (“a very wool pullover”) or as a comparative or superlative (“a more wool pullover”).
As for the attributive noun “wood,” it’s used only as a simple premodifier (“a wood floor”). It’s not used with “too” or “very,” or as a comparative or superlative.
However, the adjective “wooden” is quite flexible when used figuratively (“a wooden speech,” “a very wooden speech,” “a more wooden speech”).
Interestingly, the noun “wood” has been used since Anglo-Saxon times for the material that comes from trees, but it wasn’t used adjectivally (as either “wood” or “wooden”) until hundreds of years later.
So how did the Anglo-Saxons describe something composed of the substance that comes from the trunks, branches, and other parts of trees?
In Old English, the adjective describing a thing made of wood was tréowen, tríwen, or trýwen—from the noun tréow (“tree”) and the suffix -en (made of).
The Bosworth-Toller Anglo-Saxon Dictionary has this early example from Aelfric’s Grammar, an Old English introduction to Latin, written around 995: “ligneus, treowen.” (Ligneus is classical Latin for “wooden.”)
The Oxford English Dictionary has this example from Old English Leechdoms, a collection of medical texts written around 1000: “getrifula on treowenum mortere” (“grind in a wooden mortar”). Treowenum is the dative case of treowen. As the object of a preposition, treowenum mortere is dative.
Although this adjective is now obsolete in common usage, it survived until the late 19th century, spelled “treen” in Middle and Modern English, according to the OED. [See the update below.]
As for “wood,” it originally meant “tree” when it showed up in early Old English, spelled widu, wiodu, or wudu. The earliest Oxford example is from a Latin-Old English glossary dated around 725:
“Pinus, furhwudu.” The Latin for “pine” is translated here by the Old English for “fir tree.”
The noun “wood” soon took on the sense of a “collection of trees growing more or less thickly together,” the OED says.
The dictionary’s first citation is an excerpt in Latin and Old English from Psalm 104:11 in the Vespasian Psalter, an illuminated manuscript that the British Library dates to the second quarter of the 700s:
“Omnes bestiae silvarum, alle wilddeor wuda.” In modern English, “All the beasts of the wood.” (The full passage in the King James Version of the Bible reads: “They give drink to every beast of the field; the wild asses quench their thirst.”)
A century and a half later, the noun took on the additional sense of the “substance of which the roots, trunks, and branches of trees or shrubs consist,” the OED says.
The earliest example cited is from Pastoral Care, King Alfred’s late ninth-century translation of a sixth-century work by Pope Gregory:
“Se se ðe unwærlice ðone wuda hiewð, & sua his freond ofsliehð” (“He who carelessly hews the wood, and so slays his friend”).
The use of the attributive noun “wood” and the adjective “wooden” to describe something made of wood both showed up around the same time in the early 1500s.
The first OED appearance for the attributive noun is in a 1538 will registered in the city of York: “All wodde implementes.” (From John William Clay’s Testamenta Eboracensia: A Selection of Wills From the Registry at York, Vol. 6, 1902.)
The earliest Oxford example for the adjective is from Sir Thomas Eliot’s 1538 Latin-English dictionary: “Durateus, wodden.” The usual Latin for “wooden” is ligneus; the less common durateus comes from the Homeric Greek term for the Trojan horse, δουράτεος ἵππος (dourateos hippos, or “wooden horse”).
[Update, Aug. 23, 2018: A reader of the blog comments that “treen” still exists as a term in the field of collectible antiques. It refers to small household objects made of wood—spoons, cups, snuffboxes, shoehorns, and the like.]