Sequences
The Sequences supply for all the Acolouths of the Daily Cycle the material required for a particular Remembrance — that is to say, the material proper to a particular day of the week, a particular date of the year, a particular day in the liturgical seasons (for instance, during Great Lent or the period between Pascha (Easter) and Pentecost). These sequences can be referred to as cycles.
The fundamental element of the Sequence is the troparion, which is a short hymn, or one of the stanzas of a hymn. The kontakion is a troparion which explains briefly the character of the feast celebrated in the day's Office. The oikos is a somewhat longer troparion, which follows after the kontakion and in concise style glorifies the virtues and merits of the subject of the feast which were treated in the kontakion. The apolytikion is a troparion which is proper to the day, and is said just before the dismissal.
The ode was originally one of the nine inspired canticles sung in the morning Office, but later the name was also given to compositions consisting of a varying number of poetical troparia and modelled after the Scriptural odes. Such odes are often combined to form a canon (kanon) which is usually composed of nine, but sometimes of a smaller number of odes. Finally, the stichos is a short verse taken from the Psalms or some other book of Holy Scripture, while the sticheron is a short verse of ecclesiastical composition modelled after the stichos.
Read more about this topic: Acolouthia