The word trained is an adjective. Trained means (1) shaped or conditioned or disciplined by training; often used as a combining form.
Trained is also an adjective that means (1) having acquired necessary skills by e.g. undergoing a course of study.
The following articles and web pages elaborate on the word trained.
Browse this dog training supplies retailer directory for info about dog training supplies retailers in the United States. The photo on this web page depicts a trained dog retrieving an orange dummy.
A barista works in a coffee shop and is specially trained to prepare and serve espresso style coffee drinks. Learn more about espresso drinks and the role of baristas.
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The following digital image illustrates the word trained.