"simple vocabulary" is correct and usable in written English.
You can use it when you need to explain simple language or words in a particular context. For example, "The instructions are written in simple vocabulary so that anyone can understand them."
For some, his simple vocabulary and grammatical structure make his speeches easy to follow.
On the one hand, the president's simple vocabulary makes his words easy to follow.
Patricia Stevens, the center's principal, gave him the 15-minute exam, asking questions on simple vocabulary, letter recognition and math.
"Because she uses such simple vocabulary it isn't often noted but she is a very good technician".
The writings are varied but progress from simple vocabulary lists to a short research report on animal senses.
Simple vocabulary tests on children as young as two can identify those who will find it difficult to learn language and lag behind their peers in becoming fluent.
In another Media Lab project, Natalie Freed an alum of our group made a simple vocabulary-learning game with a robot that children and their parents played together.
Oscar tries again in simpler vocabulary.
Field-specific vocabulary demonstrate your understanding of the field and the department's needs, but be aware that Faculty Search Committees that are more mixed in expertise may require simpler vocabulary and/or explanations accessible to a broader audience.
Certain genres (such as romance) have simpler vocabularies than other genres (literary fiction, poetry).
The idea, which now seems obvious, was that children would best learn to read using absorbing, entertaining books composed in a simple, limited vocabulary.
