Yes. You can also wish someone shanah tovah u'metukah (a good and a sweet year) or l'shanah tovah tikatevu (may you be inscribed for a good year [in the book of life]) or ketivah v'chatimah tovah (a good inscription and seal), but it's not compulsory. Gam lakh is "the same to you" (fem.), I think.
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Yes. You can also wish someone shanah tovah u'metukah (a good and a sweet year) or l'shanah tovah tikatevu (may you be inscribed for a good year [in the book of life]) or ketivah v'chatimah tovah (a good inscription and seal), but it's not compulsory. Gam lakh is "the same to you" (fem.), I think.