The Hyphen ( - )

The hyphen is used mainly to separate single words which make up a compound (compound adjective: light-blue, compound noun: self-help). Not all compounds are hyphenated. For example, compound nouns may be separate words (contact lens), hyphenated words (self-help), or single terms (screwdriver). There are no rules about this; if in doubt, consult a dictionary.

Compound words

• The sound of the ocean is also a low-frequency sound.
• One important pattern-making process involves the way diffusing chemicals react with one another.
• Contrary to popular belief, predators aren’t just species with large sharp teeth or fangs, hooked beaks, or razor-sharp claws.
• But Einstein suggested that gravity was the bending of something called space-time .
• For instance, the giant, 160-km-wide Chicxulub crater in Mexico that wiped out most of the dinosaurs and many other species 65 million years ago is only 1-2 km deep and is hidden beneath younger layers of sediment.