Complex nominals (CNs) are frequently found in specialized discourse in all languages, since they are a productive
method of creating terms by combining existing lexical units. In Spanish, a conceptual combination may often be rendered with a
prepositional CN (PCN) or an equivalent adjectival CN (ACN), e.g., demanda de electricidad vs. demanda eléctrica [electricity
demand]. Adjectives in ACNs – usually derived from nouns – are known as ‘relational adjectives’ because they encode semantic
relations with other concepts. With recent exceptions, research has focused on the underlying semantic relations in CNs. In
natural language processing, several works have dealt with the automatic detection of relation adjectives in Romance and Germanic
languages. However, there is no discourse studies of these CNs, to our knowledge, for the goal of establishing writer
recommendations. This study analyzed the co-text of equivalent PCNs and ACNs to identify factors governing the use of a certain
form. EcoLexicon ES, a corpus of Spanish environmental specialized texts, was used to extract 6 relational adjectives and,
subsequently, a set of 12 pairs of equivalent CNs. Their behavior in co-text was analyzed by querying EcoLexicon ES and a general
language corpus with 20 expressions in CQP-syntax. Our results showed that immediate linguistic co-text determined the preference
for a particular structure. Based on these findings, we provide writing guidelines to assist in the production of CNs.