Satellite navigation

The tenth entry is la phase de la porteuse, and the last word in it is a single feminine form that has quietly become six English nouns. Porteur and porteuse are built on porter, to carry, and French lets the pair take on every job that verb suggests. La porteuse here is the wave that carries the modulation, « the carrier ». Un mur porteur is a load-bearing wall. Une mère porteuse is a surrogate mother. Être porteur d’un virus is to be a carrier in the medical sense, and un chèque au porteur is payable to the bearer. On a platform un porteur is a porter. English has a separate word for each and no thread running between them, so a reader who learns « carrier wave » for this entry has learned one sixth of the family and has no way of guessing the rest. The thread is worth holding on to, because it never breaks: wherever this pair turns up, something is being carried on behalf of somebody else — a signal, a floor above, a child, an infection, a debt.