What does chlorophyll mean?
Chlorophyll is the green pigment found in plants, algae, and cyanobacteria that makes photosynthesis possible. It absorbs light — chiefly in the blue and red parts of the spectrum — and channels that energy into the chemical reactions that convert carbon dioxide and water into sugars, releasing oxygen as a by-product. Because it reflects green light rather than absorbing it, chlorophyll is responsible for the characteristic green colour of leaves and other plant tissue. In autumn, as daylight shortens, plants break down their chlorophyll, unmasking the yellow and orange pigments that were present all along. The word is primarily a scientific one, appearing in botany, agriculture, ecology, and food science, where measurements of chlorophyll content serve as indicators of plant health or algal abundance. Its central role in sustaining nearly all life on Earth makes it one of the most consequential molecules in nature.
nounThe green pigment found in plants, algae, and cyanobacteria that absorbs light energy and enables photosynthesis, converting carbon dioxide and water into sugars while releasing oxygen.
- The green pigment in plants, algae, and cyanobacteria that captures light energy for photosynthesis.
"As autumn approached, the chlorophyll in the maple leaves began to break down, revealing the oranges and reds beneath."
"Chlorophyll allows plants to convert sunlight into chemical energy through photosynthesis."
"Scientists measured the chlorophyll content of the lake water to estimate algal growth."
Chlorophyll is an uncountable mass noun with no plural form; quantities are expressed as 'amounts of chlorophyll' or 'chlorophyll levels'.
"The samples differed markedly in their chlorophyll levels."
Chlorophyll is why plants are green — it absorbs red and blue light but reflects green straight back at your eyes.
Reviewed by Deb Chak, Editor. AI-assisted content curated by RJS Tech Solutions LLP.
Etymology of chlorophyll
The word chlorophyll was coined in the early nineteenth century from Greek roots: chloros, meaning pale green or yellowish green, and phyllon, meaning leaf. It thus literally means 'green leaf', a fitting name for the pigment that colours foliage. The same two roots recur across scientific vocabulary: chloros appears in chlorine and chloroplast, while phyllon underlies words such as phyllotaxy and sycophant (originally a 'fig-shower'). Chlorophyll was identified as the active agent of photosynthesis as chemists and botanists worked out the mechanism of the process during the nineteenth century.
How chlorophyll is actually used
A technical scientific term used chiefly in biology, botany, and chemistry, but familiar to most educated readers. It is an uncountable mass noun; 'a chlorophyll' is not standard, though different types may be referred to as chlorophyll a, chlorophyll b, and so on.
Easily confused with chlorophyll
Chlorophyll is the green pigment itself, whereas a chloroplast is the organelle within plant cells that contains chlorophyll.