The industrial and scientific revolutions created a need for neologisms to describe the new creations and discoveries. For this, English relied heavily on Latin and Greek. Words like oxygen, protein, nuclear, and vaccine did not exist in the classical languages, but they were created from Latin and Greek roots. Such neologisms were not exclusively created from classical roots though, English roots were used for such terms as horsepower, airplane, and typewriter.
This burst of neologisms continues today, perhaps most visible in the field of electronics and computers. Byte, cyber-, bios, hard-drive, and microchip are good examples.
Also, the rise of the British Empire and the growth of global trade served not only to introduce English to the world, but also to introduce words into English. Hindi, and the other languages of the Indian subcontinent, provided many words, such as pundit, shampoo, pajamas, and juggernaut. Virtually every language on Earth has contributed to the development of English, from Finnish (sauna) and Japanese (tycoon) to the vast contributions of French and Latin.
The British Empire was a maritime empire, and the influence of nautical terms on the English language has been great. Words and phrases like three sheets to the wind and scuttlebutt have their origins onboard ships.
Finally, the 20th century saw two world wars, and the military influence on the language during the latter half of this century has been great. Before the Great War, military service for English-speaking persons was rare; both Britain and the United States maintained small, volunteer militaries. Military slang existed, but with the exception of nautical terms, rarely influenced Standard English. During the mid-20th century, however, virtually all-British and American men served in the military. Military slang entered the language like never before. Blockbuster, nose dive, camouflage, radar, roadblock, spearhead, and landing strip are all military terms that made their way into standard English.