of the contrast of sounds between (Ng, a surname) (/ in Guangzhou pronunciation) and (not) (/ in Guangzhou pronunciation). In Hong Kong, both words are pronounced as the latter. Lastly, the initials and can be merged into and when followed by . An example is in the word for country (), pronounced in standard Guangzhou as gwok but as gok with the merge. Unlike the above two differences, this merge is found alongside the standard pronunciation in Hong Kong rather than being replaced. Educated speakers often stick to the standard pronunciation but can exemplify the merged pronunciation in casual speech. In contrast, less educated speakers pronounce the merge more frequently. Less prevalent, but still notable differences found among a number of Hong Kong speakers include: Merging of initial into null initial. Merging of and codas into and codas respectively, eliminating contrast between these pairs of finals (except after and ): -, -, -, -, - and -. Merging of the rising tones ( 2nd and 5th). Cantonese vowels tend to be traced further back to Middle Chinese than their Mandarin analogues, such as M. /aɪ/ vs. C. /ɔːi/; M. /i/ vs. C. /ɐi/; M. /ɤ/ vs. C. /ɔː/; M. /ɑʊ/ vs. C. /ou/ etc. For consonants, some differences include M. /ɕ, tɕ, tɕʰ/ vs. C. /h, k, kʰ/; M. /ʐ/ vs. C. /j/; and a greater syllable coda diversity in Cantonese (such as syllables ending in -t, -p, or -k). Tones Generally speaking, Cantonese is a tonal language with six phonetic tones, which is two more than the four in Standard Chinese Mandarin. This makes Cantonese in general more difficult to master due to required ability of users to readily be able to process two additional phonetic tones. People who grew up using Cantonese tones can usually hear the tonal differences with no problem, but adults who were brought up speaking non-tonal languages such as English and most Western European languages may not be able to distinguish the tonal differences quick enough to optimally utilise the language. This difficulty also applies to tonal language speakers with fewer tones attempting to master languages with more tones such as Mandarin natives trying to learn spoken Cantonese as adults. Historically, finals that end in a stop consonant were considered as "checked tones" and treated separately by diachronic convention, identifying Cantonese with nine tones (). However, these are seldom counted as phonemic tones in