In the neutral declarative sentence, Spanish organizes information with subject, verb and complement in a canonical order, and circumstantial complements tend to be placed at the end or moved to the beginning according to emphasis. Subordinate clauses are integrated into that structure as constituents of the main clause and can occupy the place of a noun, an adjective or an adverb. To compare their basic position with that of the simple sentence, it is convenient to relate this organization to Clause Structure and Word Order.

ElementoElement	PosiciónPosition	FunciónFunction	EjemploExample
SujetoSubject	InicialInitial	Nombra al participante principalNames the main participant	La profesora explica la lecciónThe teacher explains the lesson
VerboVerb	CentroCenter	Expresa la acción o estadoExpresses the action or state	La profesora explica la lecciónThe teacher explains the lesson
ComplementoComplement	Después del verboAfter the verb	Completa el sentido verbalCompletes the verbal sense	La profesora explica la lecciónThe teacher explains the lesson
CircunstancialCircumstantial	Final o inicialFinal or initial	Sitúa la acción en tiempo, modo o lugarPositions the action in time, mood or place	Ayer la profesora explicó la lecciónYesterday the teacher explained the lesson

Noun subordinate clauses serve the function of a noun and appear when a verb or an expression of judgment, desire, doubt, or command requires a complete proposition introduced by que or si, or by an indirect interrogative. They can function as subject, direct object, prepositional complement or term of a preposition, and their verb is usually in indicative or subjunctive depending on the speaker's attitude and the degree of volition, doubt or valuation. Their recognition depends on the main clause being incomplete without that proposition, and their punctuation aligns with the syntactic relation they establish with the main clause.

IdeaIdea	EjemploExample
Verbo rectorGoverning verb	Quiero que vengas prontoI want you to come soon
DudaDoubt	No sé si llega hoyI don't know if he arrives today
DeseoDesire	Espero que termine bienI hope that it ends well
PreposiciónPreposition	Me alegro de que estés aquíI'm glad that you're here
Interrogativa indirectaIndirect interrogative	Pregunto qué necesitaI ask what he needs
SubjuntivoSubjunctive	Es posible que lluevaIt is possible that it rains

Relative subordinate clauses modify a preceding noun and function as an adjective within the main clause. They are introduced with pronouns such as que, quien and cuyo, and in colloquial speech the relative pronoun can be omitted when it acts as the direct object. The explanatory relative clause adds incidental information and usually goes between commas, while the restrictive specifies the referent and normally does not use commas; in Peninsular Spanish and general usage in the Americas the distribution of commas can have normative nuances.

IdeaIdea	EjemploExample
EspecificativaRestrictive	El libro que compraste es nuevoThe book you bought is new
ExplicativaExplanatory	Mi hermano, que vive en Lima, llega mañanaMy brother, who lives in Lima, arrives tomorrow
QuienWho	La persona quien llamó dejó un mensajeThe person who called left a message
CuyoWhose	La autora cuyo ensayo leí ganó un premioThe author whose essay I read won a prize
ElisiónEllipsis	El coche que vi ayer ya no estáThe car I saw yesterday is no longer there

Adverbial subordinate clauses express cause, purpose, time, condition or consequence, and are equivalent to a circumstantial complement of the main clause. They may precede or follow the main clause, and their position shifts the informational focus without changing their function. Subordinating connectors clearly mark the logical relation between the two propositions, and their choice affects the temporal, causal or hypothetical value of the structure.

IdeaIdea	EjemploExample
CausalCausal	No salí porque llovíaI didn't go out because it was raining
FinalPurpose	Estudia para que apruebesStudy so you pass
TemporalTemporal	Cuando llegues, llamoWhen you arrive, I call
CondicionalConditional	Si estudias, aprendesIf you study, you learn
ConsecutivaConsecutive	Estaba tan cansado que se durmióHe was so tired that he fell asleep

The relation between the main clause and the subordinate determines the presence or absence of a comma, and punctuation helps to recognize which information is central and which is incidental. Explanatory relatives and many fronted subordinate clauses are usually separated by a comma, while restrictive (specificative) and closely bound completive clauses normally do not take it. The choice between a comma and no comma also influences the rhythm and the interpretive sense of the sentence.

IdeaIdea	EjemploExample
Explicativa con comaExplanatory with comma	Madrid, que tiene muchos museos, recibe visitantesMadrid, which has many museums, receives visitors
Especificativa sin comaRestrictive without comma	Los alumnos que llegaron temprano entraronThe students who arrived early entered
Subordinada inicialInitial subordinate	Cuando termine, te avisoWhen I finish, I will let you know
Subordinada integradaIntegrated subordinate	Dijo que vendría mañanaHe said he would come tomorrow

Negation inside the subordinate clause is usually placed in front of the negated verb, and in structures with several negative elements Spanish maintains negative concord consistently. When negation affects the subordinate clause and not the main one, only that proposition changes polarity, so the scope of 'no' should be interpreted precisely. This distribution of negation is especially important in noun and adverbial clauses introduced by connectors such as que or si.

IdeaIdea	EjemploExample
Negación internaInternal negation	Espero que no llegues tardeI hope that you don't arrive late
Alcance limitadoLimited scope	No creo que vengaI don't think he will come
Elemento negativoNegative element	Nadie dijo que no supieraNobody said that I didn't know
Polaridad de siPolarity of if	No sé si no vendráI don't know whether he will not come

In many contexts, a complete subordinate clause can alternate with an infinitive or a gerund when the subject is shared or the content is sufficiently recoverable from context. The infinitive is common after verbs of obligation, possibility or preference, while the gerund provides simultaneity or manner of development. These substitutions belong to both formal and colloquial registers, but they do not maintain exactly the same syntactic or informative nuance as a finite subordinate clause.

IdeaIdea	EjemploExample
InfinitivoInfinitive	Quiero salir tempranoI want to leave early
GerundioGerund	Entró sonriendoHe entered smiling
Equivalencia parcialPartial equivalence	Decidió irseHe decided to leave
Registro corrienteCommon usage	Prefiero esperarI prefer to wait

Noun, relative, and adverbial subordinate clauses expand the main sentence without breaking its basic architecture, and their identification depends on the governing verb, the connector and the function they perform. The canonical order remains subject, verb and complements, but subordination allows reorganizing information via fronting, postposition and punctuation. Correct reading requires distinguishing between main and subordinate clauses, recognizing the syntactic function of each, and appreciating the nuances of commas, negation, and alternation with non-finite forms.