Deep embedding of subordinate clauses

Deep embedding, or l'enchâssement (also referred to as l'emboîtement), allows for a hierarchical organization of information. To become proficient in this structure, one must respect specific syntactic rules.

1. Structural Hierarchy and Register
Basic embedding (1-2 levels) is common in all registers (e.g., 'Je sais que tu viens' - 'I know that you are coming'). Chaining three or more clauses is also very common in everyday speech (e.g., 'Je crois qu'il a dit qu'il voulait que tu viennes' - 'I believe he said he wanted you to come'). It is only excessive or clumsy embedding, known as style lourd (heavy style), that writers try to avoid. To fix deep clause chaining, one must usually use an infinitive transformation, rewrite, or break up the sentence. This is distinct from having a 'heavy subject' (sujet lourd) inside a single embedded clause, which can sometimes be resolved using stylistic inversion.

2. Mandatory Subordinators
French is much stricter than English regarding subordinators. You cannot omit them (unlike the English 'that'). While que is very common, subordinators also include relative pronouns (like qui, dont, où) and other conjunctions (like quand or parce que). In coordinated structures, repeating the subordinator after 'et' or 'ou' is standard for 'que', but for other conjunctions like 'quand', 'lorsque', 'puisque', or 'comme', they are generally replaced by 'que' rather than repeated. Always remember elision (qu') before vowels.

3. Coordinating Subordinate Clauses with 'Que'
A standard rule in complex embedding occurs when coordinating two subordinate clauses introduced by conjunctions like si, quand, lorsque, puisque, or comme. Instead of repeating the conjunction, the second clause is introduced by que. The mood of the verb depends on the original conjunction: 'si... et que' traditionally takes the subjunctive (e.g., 'Si tu viens et que tu sois en retard...' - 'If you come and you are late...'), though the indicative is also admitted and correct (note that strict teachers and standardized tests often treat the indicative here as an error, so the subjunctive is heavily preferred in formal writing and exams). However, 'quand/puisque... et que' retains the indicative (e.g., 'Quand il pleut et qu'il fait froid...' - 'When it rains and it is cold...'). If the original conjunction already requires the subjunctive (e.g., bien que, pour que), the coordinated que naturally retains the subjunctive.

4. Mood Selection and 'Attraction Modale'
Normally, each verb's mood is determined by its direct parent. However, in advanced French, attraction modale may occur. This is when a nested clause 'catches' the subjunctive from a higher clause because it shares the same 'subjective thought' or uncertainty, even if its own trigger would normally require the indicative. For example, in 'Il faut que tu trouves une excuse qui soit crédible', the verb soit is in the subjunctive by modal attraction to the subjunctive trouves.

5. The 'Ne Explétif' in Nested Clauses
In advanced embedding, you will frequently encounter the ne explétif. When a higher clause expresses fear or prevention, this non-negative 'ne' often appears in the subordinate subjunctive clause, even when nested deeply (e.g., 'Je sais qu'elle craint que tu ne viennes' - 'I know that she fears that you might come'). Note that expressions of prevention also trigger it in complex chains (e.g., 'Il a fermé la porte pour éviter que le chien ne sorte quand tu arriveras' - 'He closed the door to prevent the dog from getting out when you arrive').

6. The Infinitive Transformation
To avoid overly deep embedding, French strongly prefers or requires an infinitive construction when the subject of the main clause and the subordinate clause are the same. For example, instead of a heavy chain like 'Il dit qu'il pense qu'il partira', you would use 'Il dit qu'il pense partir' ('He says that he thinks he will leave').

7. Avoiding 'Cascades de que'
A well-known stylistic flaw is the 'cascade de que'—repeating 'que' across multiple nested levels, which makes sentences heavy and hard to read. Writers avoid this by using nominalization, infinitives, or restructuring the sentence.

8. Sequence of Tenses (Concordance des temps)
A critical rule for deep embedding is the sequence of tenses. The tense of the subordinate clause is strictly dictated by the tense of the main clause. When the main clause is in a past tense, it forces tense shifts in the embedded clauses (e.g., present becomes imperfect, future becomes conditional).

9. Usage
This pattern is primarily found in legal texts, academic essays, and classical literature where complex logical relationships must be maintained within a single period.

10. Subjunctive in Relative Clauses after Superlatives
When a nested relative clause follows a superlative or an absolute term, it often requires the subjunctive to express subjectivity or a personal judgment, even at the end of a long chain (e.g., 'Je crois que c'est le meilleur livre que j'aie jamais lu' - 'I believe that it is the best book I have ever read'). You can review this in subjunctive after a superlative.