Longman Dictionary of Contemporary English - strengthen

~ v 1 »FEELING/BELIEF/RELATIONSHIP« to become stronger or make something stronger  (Our friendship has steadily strengthened over the years. | strengthen sth)  (Steve's opposition only strengthened her resolve to go ahead.) 2 »TEAM/ARMY ETC« to make an organization, army etc more powerful, especially by increasing the number or quality of the people in it  (The team has been strengthened by the arrival of two Brazilian players.) 3 »MONEY« to increase in value or to increase the value of money  (The pound has strengthened against other currencies.) 4 »FINANCIAL SITUATION« to improve the financial situation of a country or company  (measures to strengthen the economy) 5 »STRUCTURE« to make something physically or structurally stronger  (Metal supports were added to strengthen the outer walls.) 6 »PROOF/REASON« to give support to a reason or an attempt to prove something  (Evidence from independent witnesses would greatly strengthen your case.) 7 »WIND/CURRENT« to increase in force  (The wind had strengthened during the night.)