I would call them “palabras clave”. There are probably other forms of expressing the idea, but I think the term “clave” fits here very well.


http://slideplayer.com/slide/9727779/

Power Words Content: Writing Development Grade Level: Third grade, ESOL and ESE students in any grade Curriculum Standard: The student uses multiple strategies to develop grade appropriate vocabulary. LA.3.1.6.1. The student will use new vocabulary that is introduced and taught directly. Delivery of practice: Power Words are vocabulary words that are introduced during a reading program. The words are introduced before the students read the book in the program, and they are identified during the reading process. The benefit of Power Words is that students can see the words being used in context and gain a personal association with the vocabulary.

http://www.telcon2013.com/wp-content/uploads/2014/03/TELCON2...
Teacher Learning for European Literacy Education

In this talk I’ll introduce a practical model for managing the specialised knowledge students encounter in schools, focusing on the power words that characterize different subjects, the power grammar that relates the concepts encoded in these words to one another and the power composition that organizes this knowledge in texts.

En esta conferencia, voy a presentar un modelo práctico para trabajar con el conocimiento especializado que los estudiantes encuentran en las disciplinas escolares, centrándome en las palabras clave (power words), características de las diferentes disciplinas, en la gramática necesaria (power grammar) para relacionar los conceptos codificados en esas palabras y los mecanismos de composición (power composition) que organizan el conocimiento en los textos.

http://edproductsupport.scholastic.com/content/techsupport/r...

POWER WORDS
Power Words are key vocabulary words in the Passage. Power Words are highlighted for students who have not yet been to the Word Zone. Students may click once on a Power Word to hear it pronounced and hear a definition. Students may also click other words in the passage to hear a pronunciation only. Power Words may also translate into the five languages that READ 180 supports.