A noun in construct state¹²⁰ does not speak about plural things in singular; rather it will say זבחי תודה (sacrifices of thanksgiving), זבחי שלמים (sacrifices of peace). And thus, when it says על זבח התודה (with the sacrifice of thanksgiving)¹²¹ – it adds the construct זבח so that one will not err and think that תודה is the name of a type of offering.

footnotes: ¹²⁰ Construct state is a grammatical structure that is common in Semitic languages like Hebrew in which two consecutive nouns indicate possession or modification of the first noun by the second noun. For instance, when the noun זבחי (sacrifices) is placed before the noun תודה (thanksgiving), it means “sacrifices of thanksgiving”. ¹²¹ Leviticus 7:12.