It’s an X-ray. Since the letter X begins with a vowel sound, we use the article "an" before the word X-ray (a type of radiation that can go through many solid objects).

It’s an X-ray. Since the letter X begins with a vowel sound, we use the article "an" before the word X-ray (a type of radiation that can go through many solid objects).

It uses an X-ray source to produce photons.

It uses a X-ray source to produce photons.

Remember, the rule for using "a" or "an" is based on the initial sound of the following word, not how it is spelled.

An X-ray machine consists of an X-ray generator and an X-ray detector.

And we always say "an X" (not "a X").

Knowing the properties of an X-ray beam is sometimes helpful.

Follow the same strategy with other abbreviations that start with X and are pronounced as separate letters. For example, we say "an XL" (eXtra Large) or "an XML" (eXtensible Markup Language).