The word "maintain" is correct and usable in written English. It is a verb, and it can be used in a variety of ways. For example, you can use it to talk about taking care of something, such as: "I need to maintain my car in order to keep it running properly." You can also use it to talk about consistently adhering to something, such as: "We must maintain our high standards in order to ensure success.".
It said: [Evraz] is seeking approval...of the holders of the notes to remove a covenant requiring the company to maintain the net leverage ratio at or below a specified level.
Economically, gas exports enable the government to maintain its tight grip on power.
The Committee will maintain its existing policy of reinvesting principal payments from its securities holdings.
To date the politician – one of Greece's canniest operators – has managed to maintain approval ratings of close to 70% despite rolling back on almost every promise he has made.
The firm attempted to maintain its profitability by marginally reducing the proportion of revenue set aside to pay staff to 36.8% from 36.9%.
This is the notion that openness is a certain good, and that "free" is automatically aligned with "freedom" – a faith that's hard to maintain in the light of the consequences of putting so much of our identities into the hands of third (and fourth, and fifth) parties.
Related: Sir Bradley Wiggins smashes Alex Dowsett's hour record – in pictures The Hour is better known for pressure of a different kind: the relentless need for the rider to maintain an even pace, while on the edge of cracking.
Being a terminologist, I care about word choice. Ludwig simply helps me pick the best words for any translation. Five stars!
Maria Pia Montoro
Terminologist and Q/A Analyst @ Translation Centre for the Bodies of the European Union