Η ουσία είναι άγνωστη.

The substance is unknown.

Breakdown of Η ουσία είναι άγνωστη.

• είμαι: to be
• άγνωστος: unknown
• η ουσία: substance

Questions & Answers about Η ουσία είναι άγνωστη.

What part of speech is each word in Η ουσία είναι άγνωστη?

• Η = the definite article (the), feminine singular nominative
• ουσία = a noun, feminine singular nominative
• είναι = the verb is / are, from είμαι (to be)
• άγνωστη = an adjective, feminine singular nominative, meaning unknown

So the structure is:

article + noun + verb + adjective
= The essence/substance is unknown

Why is it Η and not Ο or Το?

Because ουσία is a feminine noun.

In Greek, the definite article changes according to gender, number, and case:

• ο = masculine singular nominative
• η = feminine singular nominative
• το = neuter singular nominative

Since ουσία is feminine singular, it takes η:

• η ουσία = the essence / the substance

Why is άγνωστη feminine?