Pinheiro vs. pinho
Although they share the same root, the difference between pinheiro and pinho primarily lies in whether you are describing the living plant or the harvested material. While pinheiro refers to the tree standing in nature, pinho usually refers to the wood used for construction or furniture.
Pinheiro
B1This word refers to the living tree itself as a biological organism. You use pinheiro when talking about the plant found in a forest, garden, or nature park.
O pinheiro de Natal ficou lindo na sala.
(The Christmas tree looked beautiful in the living room.)
Havia um esquilo subindo no tronco do pinheiro.
(There was a squirrel climbing the pine tree trunk.)
O pinheiro manso é comum em Portugal.
(The stone pine is common in Portugal.)
Vamos plantar um pinheiro no jardim.
(Let's plant a pine tree in the garden.)
A tempestade derrubou o velho pinheiro.
(The storm knocked down the old pine tree.)
Pinho
B2This word usually describes the wood, timber, or lumber derived from the tree. You use pinho when discussing materials for furniture, floors, scents, or cleaning products.
Esta mesa é feita de pinho maciço.
(This table is made of solid pine.)
Adoro o cheiro fresco de pinho neste detergente.
(I love the fresh pine smell in this detergent.)
O chão da cabana era todo de pinho.
(The cabin floor was entirely pine.)
Precisamos de mais madeira de pinho para a obra.
(We need more pine wood for the construction.)
Ele comprou uma estante barata de pinho.
(He bought a cheap pine bookshelf.)
Summary
To choose the correct word, consider the context: if it is alive, has needles, and grows in the ground, it is a pinheiro. If it has been cut down and turned into a table, a floorboard, or a fragrance, it is pinho.