So as to (spoken): verb + mà + verb

In speech, mà between two verbs can mean "to", in the sense of "and use it to": Con cầm tiền này mà mua sữa. Take this money and buy some milk with it. The first verb is about taking, keeping or getting something; the second says what it's for.

You'll hear it mostly in offers and requests, when you hand someone something and tell them what to do with it: Anh lấy dù của em mà đi. Take my umbrella (in Hà Nội, ô). It sounds warm and practical, the voice of a parent or an older friend. About yourself it's rare: with tôi or em doing the action, để sounds more natural.

Để is the general word for "to, in order to", and it fits writing too: Tôi học tiếng Việt để nói chuyện với ba mẹ vợ. Mà is casual, joins two verbs that sit close together, and never opens a sentence the way để can.

Mà in the middle of a sentence can also mean "but, and yet". There, the two parts pull against each other; here, the second verb simply says what the first is for.