# Evaluation of English-Slovak Neural and Statistical Machine Translation
## 5 Discussion
Its translation was more accurate in both meaning and fluency; for example:  
(7)  
Source: [PERSON] called on residents to \"stay calm and cool-headed\" as the investigation continued into Tuesday's police raid. mt@ec_SMT: [PERSON] vyzval, aby zachovali pokoj a,,cool-headed\"ako presetrovanie pokracovalo utorkoveho polcajnym zasahom. eTranslation_NMT: [PERSON] vyzval obyvatefov, aby,,zostali pokojni a chladnohlavi\", ked' vysetrovanie pokracovalo v utorkovom polcajnom najazde. Reference: Po utorkovom polcajnom zasahu [PERSON] vyzval obyvatefov, aby,,zostali pokojni a nepodliehail panike.\"  
GT_SMT omitted two lexemes (\"residents\", \"cool-headed\") and numbered several errors in the agreement in the number and case (\"utorkoveho polcajnym zasahom\"). With these errors, the GT_SMT was inadequate and incomprehensible. In the GT_NMT, we can see the improvement in MT--in comparison to GT_SMT--in punctuation. Slovak uses a different method of quotation [44]. The BLEU_3 metric showed very similar results to those for the BLEU_2 metric. Again, the translation was more accurate than statistical machine translation due to the reference. This was mainly in sentences such as:  
(8)  
Source: Three officers were injured during the operation. mt@ec_SMT: Troch uradnikov boli zranene pocas prevadzky. (Back translation: Of three officers were injured during the operation.) eTranslation_NMT: Pocas operacie boli zraneni traja dostojnici. (Back translation: Three officers were injured during the operation.) Reference: Pocas operacie boli zraneni traja polcajti. Some sentences contained identical neural machine translations as a reference, i.e., all BLEU_n metrics showed higher scores in the neural machine translation than in the statistical machine translation; e.g.,  
(9)  
Source: The search for suspects continues. mt@ec_SMT: Vyh?adavanie podozrivych pokracuje. eTranslation_NMT: Patranie po podozrivych pokracuje. Reference: Patranie po podozrivych pokracuje. Both sentences are fluent and comprehensible; GT_SMT used a less adequate equivalent for the word \"search\" than GT_NMT. Similarly to GT, in the EC's tool, we also recorded a decreasing quality of the neural machine translation compared to the statistical MT. In addition the erroneous declension, untranslated words occurred in the NMT, but such a significant difference in the quality of the translation as in the GT was not proven; e.g.,  
(10)  
Source: The names of several people linked to last November's Paris terror attacks appear in a cache of leaked Islamic State documents, according to reports in Germany. mt@ec_SMT: Mena viacerych osob spojenych s minuly rok v novembri v Parizi terori-stickych utokov su vo vyrovnavacej uniku Islamskeho statu, pod'a sprav v Nemecku. eTranslation_NMT: Mena niekoIkych fudi spojenych s Pariz terroristickych uttokov november minuleho roka je uvedene cache z uniknutych dokumentov islamsky stat, podfa sprav v Nemecku. Reference: Podfa sprav z Nemecka sa mena viacerych osob spajanych s novembrovymi terroristickymi uttokmi v Parizi objavuju v mnohych odhalenych dokumentoch Islamskeho statu. The issues in the category of agreement in gender, number, and case appeared even in the last example (10). We agree with [41] that the situation with translation worsens with multi-word sentence elements and complicated sentence structures (e.g., a group of southern Pacific islands, Europe's centuries-long history, local agricultural business leaders, a positive contribution to developing an effective post-Brexit immigration policy). Through our analysis, we not only verified our assumption about the better quality of neural machine translation, but mainly through the residual analysis, we were also able to identify the texts with the greatest distance between NMT and SMT. This allowed us to focus more precisely--in terms of more detailed linguistic analysis--on texts with the greatest distances in translation accuracy between examined translation technologies.