Common words 'less likely to change'

Frequently spoken words are less likely to change over time, according to two studies of how languages evolve in response to how often a word is used in everyday situations.

One of the studies found that irregular verbs with unpredictable endings – such as "to be" – will evolve 10 times more slowly than another verb that is used 100 times less frequently.

Another study of four modern languages – English, Spanish, Russian and Greek – which all derived from the same Indo-European ancestral language – found that the most commonly used words in each language, such as the word for water, continue to share similar traits.

The study, published in the journal Nature, is based on the principles of Darwinian natural selection, and attempts to explain how languages continue to change over time.

The Harvard University team, led by mathematician Martin Nowak, analysed 177 irregular verbs used in Old English and followed their usage through to Middle English, spoken around AD1200, and then to the English of today.

They found that an irregular verb that is used 100 times less frequently than another irregular verb changes to a regular verb with a predictable "...ed" ending for the past tense 10 times faster.

Practically all irregular verbs used today are vestiges of long-abandoned rules of conjugation, whereas all modern verbs, such as "to google", are regular.

The second study by a team led by Mark Pagel of Reading University also found that less frequently used words are more likely to evolve at a faster rate when they compared 200 meanings across English, Russian, Spanish and Greek. "Across all 200 meanings, frequently used words evolve at slower rates and infrequently used words evolve more rapidly," the scientists say in Nature.