柴又称为薪，是一种燃料。一般先砍伐树木的主干或枝条，然后把它们劈成适合炉灶大小的条状木材，就是柴。柴是古人日常生活必需品、「开门七件事」“柴米油盐酱醋茶”中排首位；这里的柴泛指炊用燃料。

另外，在中国民间，又有“柴火”的叫法，这个柴火则可能不但包括用树木制作的“柴”，还包括用干枯的稻草、野草等草本植物，秸秆或树叶、木屑等物。长期以来，中国农民使用柴火，烧柴。陶渊明担任彭泽令时，送一仆人给其子，又写信说道：「汝旦夕之费，自给为难。令遗此力，助汝薪水之劳。此亦人子也，可善遇之。」薪水即是「砍柴挑水」，如今已经成了工资、报酬的代名词。

Wood fuel (or fuelwood) is a fuel, such as firewood, charcoal, chips, sheets, pellets, and sawdust. The particular form used depends upon factors such as source, quantity, quality and application. In many areas, wood is the most easily available form of fuel, requiring no tools in the case of picking up dead wood, or few tools, although as in any industry, specialized tools, such as skidders and hydraulic wood splitters, have been developed to mechanize production. Sawmill waste and construction industry by-products also include various forms of lumber tailings.