-li

Attachment and Orthography:
In modern standard Czech, -li attaches almost exclusively to the first stressed word of the dependent clause. In conditional clauses, the verb (either the finite verb or the l-participle in compound tenses) is almost always moved to the first position to host it (e.g., Prší-li dnes..., Viděl-li jsi to..., never Dnes prší-li...). It can also attach to the negative particle ne (e.g., ne-li, which is frequently used as a set phrase meaning 'if not' or 'or even', as in stovky, ne-li tisíce – 'hundreds, if not thousands'). It must be attached to its host with a hyphen (spojovník), with absolutely no spaces before or after. Because -li attaches to the first stressed word, it pushes reflexive pronouns (se/si) and other clitics to the next position (e.g., Podaří-li se vám to..., never Podaří se-li...).

Clause Position and Punctuation:
The dependent clause containing -li can freely precede or follow the main clause. As a subordinate conditional clause, it must always be separated from the main clause by a comma. While it often precedes the main clause (e.g., Bude-li pršet, zůstaneme doma.), placing it after the main clause is completely standard and very common, especially in legal, academic, and formal texts (e.g., Smlouva zaniká, nedohodnou-li se strany jinak.).

Register and Usage:
This particle is highly formal, literary, and bookish. It is still in active, everyday use in written Czech (journalism, literature, legal texts, business correspondence). However, it is almost entirely absent from casual spoken Czech, where it sounds archaic or overly dramatic.

Crucial Distinctions:

• Not a past tense suffix: Do not confuse the enclitic -li with the past tense masculine animate plural ending (e.g., muži dělali). The enclitic can attach to the l-participle (e.g., dělal-li), but it is distinguished orthographically by the mandatory hyphen and syntactically as a clitic particle.
• The -lis contraction: In literary texts, you may encounter the contraction -lis (e.g., Viděl-lis to?). This occurs when -li is used in the second-person singular past tense and the auxiliary verb jsi attaches directly to it.
• Primarily for real conditions: When used for conditions, it is almost exclusively used for real conditions. While grammatically permissible for unreal or counterfactual conditions (e.g., byl-li by...), this usage is highly archaic and clumsy. Learners should strongly prefer kdyby + kondicionál for hypothetical scenarios.
• Lexicalized conjunctions: Words like jestli, jestliže, zdali, neboli, čili, and pakliže historically absorbed the -li particle and are now standalone words. Writing them with a hyphen (e.g., zda-li) is a severe orthographic error.