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Full retraining is the default option, and is available for all types of engines. To find out more about the training process itself, see Training an engine.
When You will be presented with two options when clicking the Train button if an engine meets these criteria:
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and then you add/remove master corpora without changing the auxiliary/stock corpora selection, you will be presented with two options when you click the Train button.
If the above criteria are not met, you will have no options to choose from, and training will just start as usual.
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