Verbal noun expressing purpose or limit of action. The infinitive implies the action a potential. With an article they are used as nouns, otherwise as adjectives. The participle generally contemplates action as real. The single letter is a short hand notation for the grammar it represents.
Greek nouns use masculine, feminine, and neuter gender.
The nominative is the case of the subject. Root idea is designation. The ablative is the whence case expressed in English by 'from', 'away'. The root idea is separation. The root idea is position.