Letter: Mind your units

Although your recently published CET articles are most laudable in their attempts to develop and improve professional standards, one feels compelled to correct a common recurrent error.

Under the Système International d'Unités (SI) the noun for a given unit always starts with a lower case letter, while it may have been named after a proper noun, correctly spelt with a capital initial letter.

Often the corresponding SI symbol will also incorporate an initial capital letter.

Thus there are no such SI units as 'Newtons per square metre', or a 'Pascal' (see Contact lens material properties, optician, Nov 4 2005, p31).

The correct usage is that the SI unit newton (N) was named in honour of Newton; and the pascal (Pa) was named after Pascal.

Yours pedantically
Dr David A Woolf
Cardiff