proti + Dative

The preposition proti is a high-frequency, neutral word in Czech that serves two main functions:

• Adversarial (Against): Used for opposing an idea, a person, or a physical force (like wind or a river current).
• Spatial (Opposite/Facing): Used to describe physical orientation, such as sitting across from someone or a building facing another.

Grammar Rules:
Proti forces the following noun, pronoun, or adjective into the dative case (the 3rd case). When used with personal pronouns, remember to use their dative forms. Crucially, 3rd-person pronouns must take an n- prefix after prepositions, so you must say proti němu (against him) or proti ní (against her), never proti jemu/jí. Unlike the preposition k/ke, which changes its form to aid pronunciation, proti is phonologically stable and never changes its spelling.

Standalone Use:
While proti is primarily a preposition, it is frequently used on its own as an adverb or predicative when no noun follows. For example, you can simply say Jsem proti. (I am against it.) or ask Kdo je proti? (Who is against?).

Important Distinctions & Phrases:

• Mít něco proti / Nemít nic proti: A core conversational phrase meaning 'to have something against' or 'to have nothing against' (e.g., Nemám nic proti tobě. - I have nothing against you).
• Proti vs. Naproti: Both can mean 'opposite' (e.g., dům proti/naproti škole). While proti broadly covers both spatial and adversarial meanings ('against'), naproti is primarily spatial, though it has abstract uses like naproti tomu (on the other hand). Also note the common phrase jít někomu naproti (to go meet someone).
• Proti vs. Oproti: Oproti means 'compared to' or 'in contrast to', not 'against'.
• Proti vs. Vůči: While proti implies direct opposition or physical direction ('against', 'opposite'), vůči means 'towards' or 'in relation to' and is used for attitudes, feelings, or behaviors toward someone or something (e.g., být slušný vůči starším - to be polite towards the elderly).
• Proti vs. Pro: Beginners often confuse these. Pro means 'for' (takes accusative), while proti means 'against' (takes dative). Crucial exception: When talking about medicines or treatments, Czech uses proti (against) where English uses 'for'. For example, you must say lék proti kašli (medicine for a cough) or prášky proti bolesti (painkillers / pills for pain).
• Pro a proti: A very common fixed phrase meaning 'pros and cons', where proti acts as a noun (e.g., Musíme zvážit všechna pro a proti. - We have to weigh all the pros and cons.).
• Být někomu proti srsti: A common idiom meaning 'to go against the grain' or 'to rub someone the wrong way' (e.g., To je mi proti srsti. - That goes against the grain for me.).