[found on quickanddirtytips.com; by Bonnie Trenga Mills]
“Do you want to get ahead (one word) or are you cooking an esoteric dish and want to get a head (two words)? That one little space can make a big difference in meaning: Either you are moving past others in business or you are purchasing a skull…..
When it comes to pairs such as “apart” with no space and “a part” with a space, the spelling doesn’t matter when you’re talking; both sound the same. When you write the words, however, you might forget to add a space, or you might add an unnecessary one. This problem crops up with all kinds of words, but in this episode we’re focusing on words beginning with the letter “a.”
Words That Start With “A”
Here’s a short list of pairs like “ahead” and “a head”: “alight” and “a light,” “abuzz” and “a buzz,” “apart” and “a part,” and, lastly, “ahold” and “a hold.” As you can see from this list, the one-worders beginning with “a” can be various parts of speech: “ahead” is an adverb, “alight” is a verb,” and “abuzz” is an adjective. The two-worders, on the other hand, consist of an article—the word “a”—and a noun: “light,” “buzz,” “part,” and “hold.” True, these words can sometimes be verbs, but when something follows the article “a,” it’s a noun (unless something such as an adjective comes between the article and the noun, as in “a delicious cake”).
“Alight” Versus “A Light”
Let’s see these four pairs in action. The first two—“alight”/“a light” and “abuzz”/“a buzz”—are the easy ones. You could say, “That annoying bee wants to alight on my nose.” This means the bee wants to land on your nose, and there’s no space in “alight.” If you say, “He turned on a light”—with a space—that means he was no longer enveloped in darkness.
“Abuzz” Versus “A Buzz”
In keeping with the bee theme, here’s our next example: “I heard a buzz.” A quick test for those listening: Is there a space or not? Well, yes, there is! “A buzz” with a space means “a buzzing noise.” “Abuzz” with no space is an adjective that means alive with activity, as in “The room became abuzz when the grammarian entered.”
To read the entire article from Grammar Girl, click here.