The three similar words are merriment, laughter and hilarity—hopefully things you experience while working on this puzzle! Each four-letter word is the middle of a much bigger word. Fill in the blank ...

Some numbers are so unimaginably large that they defy the bounds of modern mathematics, and now mathematicians are closing in ...

Numbers of Arctic terns nesting at a key breeding site have dropped by nearly a third this year, as experts warn climate change and disease are hitting the rare birds.