за + Instrumental

The construction за + инструментал is an important intermediate-to-advanced pattern in Serbian, with distinct syntactic behavior that refines standard textbook rules.

1. Spatial Following vs. Directional Motion
Learners are often introduced to за taking the accusative for directional motion toward a functional workstation or behind an obstacle (e.g., сести за сто; заћи за зграду) and the instrumental for static location (e.g., седети за столом; стајати за кућом). While everyday spoken Serbian frequently uses иза + генитив (отићи иза зграде) for movement behind physical objects, за + акузатив remains fully standard for motion behind a landmark or barrier. Crucially, when a verb of motion denotes tracking or following along someone's path rather than heading toward a fixed furniture position or static hiding spot, it strictly governs the instrumental:
• Иди за мном! (Follow behind me!)
• Пас трчи за аутом. (The dog is running after the car.)

2. Sensory and Attentional Tracking
Verbs of perception use this construction when attention lingers in the wake of someone departing:
• гледати за неким (to gaze after someone / to watch someone as they walk away)
• окренути се за неким (to turn around to follow someone with one's eyes)

3. Emotional Complements (Longing, Grief, Nostalgia)
A specific set of affective verbs takes за + инструментал to denote the focus of yearning or grief. For verbs like чезнути, жудети, and туговати, the preposition за with the instrumental is the standard complement frame. However, verb government varies across other emotional predicates:
• чезнути за... (to yearn/long for...): чезнути за слободом
• жудети за... (to crave/pine for...): жудети за пажњом
• туговати за... (to mourn/grieve for...): туговати за домовином
• жалити за... (to regret/mourn for...): While жалити за младошћу expresses nostalgic longing, жалити can also govern a bare accusative for remorse or pity (e.g., жалити пропуштену прилику — "to regret a missed opportunity"; жалити новац — "to begrudge money").
• патити за... (to pine/ache for someone or something): The verb патити governs за + инструментал specifically for sentimental or romantic pining (патити за бившом љубављу), whereas physical illnesses require од + генитив (e.g., патити од несанице) and causes of distress take због + генитив (e.g., патити због неправде).

4. Pronoun Forms
When governed by за, personal pronouns appear in the instrumental case: за мном, за тобом, за њим, за њом, за нама, за вама, за њима. In addition, the reflexive pronoun себе takes the instrumental form собом (producing за собом), an essential pattern in everyday idioms referring back to the subject (e.g., Затворио је врата за собом — "He closed the door behind him"; оставити траг за собом — "to leave a trace behind oneself"). Unlike the genitive, dative, and accusative, the instrumental in Serbian has no clitic (unstressed) pronoun forms at all.

Pay close attention to pronoun endings: for the 1st person singular pronoun (ја), the distribution is strictly complementary—мном is mandatory after prepositions (за мном, са мном), while *за мноме is ungrammatical (the form мноме is restricted to bare instrumental contexts). For third-person pronouns (он/оно and она), contemporary standard usage strongly favors the shorter forms after prepositions (за њим, за њом), whereas the longer forms with mobile -е (њиме, њоме) are primarily used in the bare instrumental without a preposition (e.g., Поноси се њиме).