Sūtra 1-26
स एष पूर्वेषामपि गुरुः कालेनानवच्छेदात्। (२६)
Sa eṣa pūrveṣāmapi guruḥ kālenānavachedāt.
(Saḥ eṣaḥ pūrveṣām api guruḥ kālena anavachedāt) (26)
(He is) also the foremost Teacher since He is not conditioned by Time.

Sūtra words
Saḥ, eṣaḥ, pūrveṣām, api, guruḥ, kālena and anavachedāt

Word Formation
Saḥ — First case singular, masculine gender form of the pronoun tat
eṣaḥ — First case singular, masculine gender form of the pronoun etat
pūrveṣām — Sixth case plural, masculine gender form of the pronoun pūrva
api — Indeclinable, a form that does not change in number, gender, case, person, tense or mood
guruḥ — First case singular, masculine gender form of guru  (verb) gṝ + (suffix) u 
kālena — Third person singular, masculine gender of the noun kāla (verb) kal + (suffix) a
anavachedāt — Fifth case singular, masculine gender of the noun anavaccheda. Avaccheda  (verb) chid + (prefix) ava + (suffix) a.
Anavaccheda  (na)+avaccheda = an+avaccheda
(This form of a compound is called nañ-tatputuṣa. The negative particle na that changes to an when followed by a vowel beginning word) 

Meaning of words
Saḥ eṣaḥ — The first two words Saḥ and eṣaḥ are omitted in many versions of this aphorism. This is a style in Sanskrit, literally meaning “This, He”. It is used to indicate a person who was mentioned earlier, in this instance, in the prior aphorism. We translate is simply as He.
pūrveṣām — Compared to those prior (previous, earlier teachers)
api — even
guruḥ — teacher
kālena — by time
anavachedāt — because not limited
The translation captures the meaning, not a literal word meaning. Īśvara, unlike all the teachers starting from Patañjali to the endless line of teachers before him who had dates of birth and death, is not limited by time.