The ability to understand and use a particular language. It is very often used in the plural ('Sprachkenntnisse') to describe the entirety of a person's language abilities.
example
Für diese Stelle sind verhandlungssichere Englischkenntnisse erforderlich.
Business-fluent English skills are required for this position.
Usage tips
Compound word
The word is made up of 'Sprache' (language) and 'Kenntnis' (knowledge). A 'Kenntnis' is knowledge about something, so the word literally describes knowledge of a language.
EXAMPLE
Gute Sprachkenntnisse sind in vielen Berufen ein großer Vorteil.
Good language skills are a major advantage in many professions.
Plural is the norm
Although there is a singular form, the word is almost always used in the plural 'Sprachkenntnisse' (language skills). This describes overall ability in one or more languages. The singular 'die Sprachkenntnis' (language skill) is rare and rather formal.
EXAMPLE
Bitte geben Sie Ihre Sprachkenntnisse im Lebenslauf an.
Please list your language skills on your resume.
Typical collocations
Adjectives are often used to describe the level of ability. Typical combinations are: grundlegende, gute, fließende, verhandlungssichere, or perfekte Sprachkenntnisse (basic, good, fluent, business-fluent, or perfect language skills).
EXAMPLE
Für den Anfang reichen grundlegende Sprachkenntnisse.
Basic language skills are enough to start with.
Preposition 'in'
To name the language in which someone has skills, you use the preposition 'in' followed by the dative. So you have Sprachkenntnisse in Deutsch, in Englisch, in Spanisch, etc. (language skills in German, in English, in Spanish, etc.).
EXAMPLE
Sie hat sehr gute Kenntnisse in der spanischen Sprache.
She has very good knowledge of the Spanish language.