It is not necessary that every professional proves to be a professional translator. If you want your medical text to be translated, it is NOT steadfast law that every doctor will be a good choice for converting your medical document into a foreign language.
Punctuality/Meeting Deadlines
You will find many linguists who are qualified, educated, expert, and experienced but NOT punctual. Punctuality is a very necessary characteristic. However, you can also hire professional translators at https://translationsandinterpretations.com.au/services/translating/.
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It makes qualified a Professional. If the translator lacks punctuality, you can say "he is qualified" but you can't say (in my personal opinion) "he is a professional".
Qualification + Education + Experience – Punctuality = UN PROFESSIONAL
Proficiency in Both, Source & Target Language
Translator must have a very strong grip on both languages. Always hire the one who is native in target language.
Native translator is always better than non-native, keeping in account the qualification and experience. The translated text will always show weakness if translated by a non-native.
Under certain circumstances, you can hire non-natives, where the native speaker is not available or where the translator is not native but he spent years in country + company of native speakers.
Beware of Literary Document
When it comes to translation of any piece of art, writings of great writers & works of prominent poets you should be careful.
Never ever forward such kind of project to a translator who hasn't translated such text before. It is not necessary that a linguist with medical experience of 10 years is competent enough to translate such text. In conclusion, your recruitment process needs to be very cautious.