This word is acceptable for play in the US & UK dictionaries that are being used in the following games:

• Lexulous
• Wordscraper
• Wordosaur

n. The property of being single.

n. The result or product of being single.

n. The quality or state of being single, or separate from all others; the opposite of doubleness, complication, or multiplicity.

n. Freedom from duplicity, or secondary and selfish ends; purity of mind or purpose; simplicity; sincerity.

n. The state or character of being single, in any sense of the word.

n. without hypocrisy

n. the quality of concentrating on one central objective

"That thing we call singleness of heart and mind is a dread thing to behold."

multiplicity    manyness   

sincerity    assiduity    concentration    assiduousness   

oneness   

simplicity    sincerity    celibacy   

oneness    uprightness    steadfastness    fearlessness    steadiness    wholeness    definiteness    single-mindedness    truthfulness    disinterestedness