The best way to use a phrasebook is to use it for just reviewing those words that you more or less understand. Although there's usually more than one definition provided to a single word, more is needed because there's more to a word than its meanings, such as formality. We can't measure exactly when it's appropriate to use a particular phrase by looking at its often arbitrarily chosen definition. In a nutshell, Memorising a word and its meanings by a phrasebook inevitably creates a gap between your understanding and its actual use. A single phrasebook simply doesn't provide enough information to grasp the totality of words.

However, using a phrasebook containing phrases you're already familiar with is recommended because it helps reinforce your memory. As we continue our language study, we encounter the same word used in many different sentences, and that's how we usually accumulate information about that word. A phrasebook is effective if you've seen or heard the word several times, and it strengthens the existing knowledge about it.