The phrase "a single cup" is correct and usable in written English.
You can use it when referring to one cup, often in contexts related to beverages or measurements.
Example: "I only need a single cup of coffee to start my day."
Alternatives: "one cup" or "just a cup".
People in New York, Paris and Tokyo may pay almost that much for a single cup.
"We brought only a single cup to drink with and some red pepper.
The jobless often sat out cold winter days nursing a single cup of automat coffee for hours.
"As per our information, not a single cup of black tea was drunk in Afghanistan," he said.
Talking with a great deal of intense energy, he used three tea bags for a single cup of tea.
I can't wait for the inevitable Still biopic: a self-important iceberg doling out a single cup of coffee as he expounds on his own greatness.
C. reinhardtii is an approximately 10-μm, unicellular, soil-dwelling green alga with an eyespot, a nucleus, multiple mitochondria, two anterior flagella for motility and mating, and a single cup-shaped chloroplast that accommodates the photosynthetic apparatus [86, 87].
Each Chlamydomonas cell has a single, cup-shaped chloroplast.
This marine unicellular green alga exhibits a counterclockwise arrangement of basal bodies [ 19, 20] and a single cup-shaped chloroplast [ 20].
In C. reinhardtii, a single cup-shaped plastid takes up over two thirds of the total cellular volume when cultivated under nutrient replete conditions [ 21], where neither starch granule nor lipid bodies could be detected.
Chlamydomonas cells are ∼10 μm in diameter, and about half of their volume is occupied by a single cup-shaped chloroplast (Sager and Palade, 1957; Gaffal et al., 1995).
