For the noun denoting animals of the phylum Mollusca---which includes squid, octopuses, slugs, and snails---mollusk is the preferred spelling in North America, and mollusc is preferred throughout the rest of the English-speaking world. The word came to English from the French mollusque (which in ... Read more
Sulfur vs. sulphur
For the pale yellow nonmetallic element found especially in volcanic deposits, sulfur is the usual spelling in American English. Sulphur is generally the preferred spelling in nonscientific texts from outside North America, but sulfur is gaining ground in scientific writing throughout the ... Read more
Phosphorous vs. phosphorus
Phosphorus denotes the chemical element (with the symbol P and the atomic number 15) present in a few types of minerals found on Earth. It comes from a Latin word for morning star, and it is so named because it glows when exposed to oxygen.1 Phosphorous (note the o in the last syllable) is an ... Read more
Aluminium vs. aluminum
Aluminum is the American and Canadian spelling for the silver-white metallic element (number 13 on the periodic table) abundant in the earth's crust. Aluminium is the preferred spelling outside North America. Neither term is superior to the other, and both are etymologically and logically ... Read more
Sceptic vs. skeptic
In most of their senses, there is no difference between skeptic and sceptic. Skeptic is the preferred spelling in American and Canadian English, and sceptic is preferred in the main varieties of English from outside North America. This extends to all derivatives, including sceptical/skeptical and ... Read more
