If you act faithfully, you continue to support a person, organization, idea, or activity for a long time.
He has since 1965 faithfully followed and supported every twist and turn of government policy.
他从1965年起忠实地追随并支持政府政策的每一次重大转变。
If you translate or copy something faithfully, you accurately represent or reproduce the original.
When I adapt something I translate from one meaning to another as faithfully as I can.
我在改编的时候,我用尽量忠实于原文的方式把一种含义翻译为另一种。
When you start a formal or business letter with 'Dear Sir' or 'Dear Madam', you write Yours faithfully before your signature at the end.