for a moment,“為一片刻”,是指片刻、一會兒或一段簡短的時間
簡單用法：
wait for a moment 等一會兒
come here for a moment 過來一下
for the moment,“為那時刻”,是指那時、那一刻,帶有強調(diào)、特指的性質(zhì).
簡單用法：
wait for the moment to come 等那時刻來臨
They have their reasons for keeping their marriage a secret for a moment.
他們有自己的原因,暫時將他們倆的婚姻保守秘密.
點評：這里for a moment可理解為暫時,即短時間的意思.
for a moment是在修飾keepingXXX a secret,這段短語.
They have their reasons for keeping their marriage a secret for the moment.
他們有自己的原因,將他們倆婚姻的那一刻保守秘密.
點評：這里for the moment可理解為某某事件的那一顆,即短時間的意思.不過,全句并不通順,寫成如下較為通順,但意思又變了.
They have their reasons for keeping their marriage a secret down/solely for the moment.
或
They have their reasons for keeping their marriage a secret till the moment.
(他們有自己的原因,將他們倆婚姻保密到來領(lǐng)的那一刻.)