Stress is shown by the high stress mark (ˈ) before the syllable with the main stress, and by the low stress mark (ˌ) before any syllable with a secondary stress.
See also the chart for British English and the foreign sounds list.
Unlike in the UK, dictionaries published in the US do not usually use the IPA for their pronunciation keys, so there is no established standard transcription scheme. This one is taken from Kretzschmar Jr., William A. (2006) ‘Pronunciation Keys in American Dictionaries’ in Dictionaries: Journal of the Dictionary Society of North America 27, in the hope of establishing it as a standard. In its favour is that it is relatively simple and is easy to learn even for those who are used to the various existing non-IPA schemes used in American dictionaries. Against it is that it is quite dissimilar to the standard scheme for British English. (As a traditionalist I also object to the use of ‹ə› for strong vowels, but this is common among American phoneticians.)
Unfortunately the system is not very well-described in Kretzschmar’s paper, and I have had to make some assumptions about how the system works that may not reflect his actual intentions
Key words for consonants are selected from the most 1,000 frequent words in the Moby word list and the COCA word frequency data, favouring appearances in word-initial position. Key words for vowels are the standard lexical sets, with the exception of fire, power, and situation, which are from Wells.