Health care, healthcare or health-care? Make up, makeup or make-up? Water ski, water-ski or waterski? Cell phone, cellphone or cell-phone? A lot of questions posed in this column elicit the answer: ...

According to my 1933 Oxford Universal Dictionary, “good-bye” and “co-operate” are hyphenated, neither “leg room” nor “birth rate” can be run together into single word, and “teenager” doesn’t exist.

Even the sticklers who can spot a stray apostrophe a mile off may struggle over when to use a hyphen. But help is at hand for those who are unsure of where to put one. A study of more than 10,000 ...