Nouns are name words: for physical things (tree, house, person) or for ideas or concepts (justice, love, righteousness). Proper nouns name a specific person or place and begin with a capital letter (Mary, Peter, Rome, Corinth).
In Greek, the noun consists of a stem plus endings (like the verb in this respect).
The endings show the function the word is performing in the sentence. We’ll start off with two functions: subject and object.
If the word is the subject, it is doing the action of the verb e.g.
The dog is barking.
The verb is barking. What is doing the barking? The dog – so the dog is the subject of the verb.
If the word is the object, it is suffering (in grammatical terms) or undergoing the action of the verb e.g.
Peter strokes the dog.
The verb is strokes. Who is doing the stroking? Peter, so he is the subject. Peter strokes what? - The dog, therefore the word dog is the object of the verb strokes.
Jesus sends out apostles. The verb is sends out. Who is doing the sending? Jesus, therefore, Jesus is the subject of the verb. Jesus sends out what? Apostles, therefore the word apostles is the object of the verb sends out.
If a noun is acting as the subject of a verb, the form it takes is called the nominative case. This is the form in which you will find it listed in the lexicon.
If a noun is acting as the object of a verb, the form it takes is called the accusative case.
There are three genders for nouns in Greek: masculine, feminine and neuter. This need not have anything to do with the actual gender of the word; for instance, the word for woman, γυνή, is feminine as you might expect; but so is the word for day, ἡμέρα . Nouns in Greek are grouped into three classes called declensions.
Traditionally Greek grammars always start with the second declension, which contains a very large collection of commonly occurring nouns. The second declension has one masculine and one neuter pattern in it; nouns following these patterns are grouped together in one declension because there is a family resemblance in the way they form their case endings.
The pattern word Duff begins with is λόγος: a 2nd declension, masculine pattern.
All nouns that follow this pattern will end in –ος. To get to the stem, chop off the –ος . For example:
ἄγγελος means messenger or angel. To form the nominative plural, angels, remove the –ος and add –οι, to give ἄγγελοι.
You will need to learn the paradigm in Duff, p25.
It sounds like this:
Repeat this to yourself until you know it by heart.