Between “singley” and “singly,” the correct spelling is singly. It’s the standard English adverb meaning individually or one at a time. “Singley” does not appear in any major dictionary and is almost always a misspelling. The only time the “-ey” spelling is correct is when it refers to a surname.
What “Singly” Means
“Singly” describes doing something as a single unit, without others, or one at a time. If a teacher calls students to the front singly, each one goes up alone. If packages move through inspection singly, they are checked one by one rather than in batches. The word carries a sense of deliberate separation: things happening singly are kept apart on purpose.
Close synonyms include “individually,” “separately,” “alone,” and “one by one.” “Singly” emphasizes the one-at-a-time aspect more sharply than most of its alternatives.
Where You’ll See “Singly” Used
Legal documents use “singly” when something applies to each party on its own rather than to a group. A corporate resolution might authorize officers to sign contracts “singly or jointly,” meaning any one officer can act alone or two can act together. The distinction matters in liability too. Under joint and several liability, a plaintiff can collect the full value of a judgment from any one defendant individually, and that defendant can then seek reimbursement from the others.1LII / Legal Information Institute. Joint and Several Liability
The word also does work in the sciences. A “singly ionized” atom in physics has lost exactly one electron. A “singly linked list” in computer science is a data structure where each element points forward to the next but not back. Across these fields, “singly” means the same thing it does in ordinary English: exactly one.
When “Singley” Is Actually Correct
“Singley” does not appear in standard dictionaries. When it shows up in writing, the extra “e” before the “y” is usually a mistake. The error probably creeps in because English has plenty of common words with “-ey” endings, such as “money,” “donkey,” and “turkey,” which makes “singley” look plausible at a glance.
The one legitimate use of “Singley” is as a surname. Roughly 3,800 people in the United States carry the name, with the highest concentrations in Pennsylvania, California, and Georgia. If you see “Singley” capitalized and referring to a person, a family, or a business named after someone, the spelling is fine. Everywhere else, you want “singly.”
Both forms sound identical, with stress on the first syllable and a hard “g” in the middle. You cannot tell the misspelling from the correct form by ear, which is part of why it persists in writing.
A Quick Spelling Check
Start with “single.” Drop the final “e” and add “-ly.” That gives you “singly,” following the same pattern as other English adverbs built from adjectives ending in “-le”: simple becomes simply, gentle becomes gently, humble becomes humbly. The root never picks up an extra letter.
If you catch yourself typing “singley,” ask one question: are you writing about a person’s name? If the answer is no, delete the “e.” The adverb is always “singly,” and the only time that extra vowel belongs is on a nameplate or an envelope addressed to someone in the Singley family.